Chuck Cunningham Syndrome / Professional Wrestling
This happens regularly. Wrestlers leave the company, which is very rarely acknowledged on the air; the sole reference will generally be in a short corporate press release stating that they and the company have come to terms on their departure and that WWE "wishes them the best in their future endeavors" — leading to the popular Fan Speak term for a wrestler being fired: being 'future-endeavored'. They may be taken off the air prior to leaving, to lower their 'drawing' value. Usually this happens to guys who work the lower matches, and so flies under the radar, but occasionally even a big name will simply vanish. For example, Sable, who was extremely popular in the late '90s, abruptly vanished from programming — because she sued the company. Similarly, Eric Bischoff was taken off the air in WCW for his inept management, and his on-air departure was never acknowledged, which made it even less understandable when he returned in April 2000.
A particularly egregious example was when 1980s megastar Hulk Hogan left the WWF in 1993. After losing the WWF title to Yokozuna at King of Ring, Hogan was never mentioned again until wrestling started taking on more 'realistic' angles.
This appears to have once again happened with the Hulkster in 2015. He was a host on Tough Enough and appeared sporadically on other WWE programs but was abruptly fired for making racially offensive comments. WWE even went to the point of erasing him from the Hall of Fame portion of their websitenote the company has never stated whether or not this means that he has been expelled from the Hall of Fame itself, but given that it lacks a physical location, one can forgive the confusion and its upcoming WWE '16 game where he would have figured prominently.
One of the worst examples of this happening was the managers of "Stunning" Steve Austin after he first entered WCW in 1991. When he debuted, he was accompanied by a brunette named Vivacious Veronica, however after a few weeks she was replaced without explanation by a blond called Lady Blossom (who was Austin's then wife and former WCCW valet, Jeannie Clark), about a year later she disappeared and Paul E. Dangerously (AKA Paul Heyman) took over the job of managing Austin. Madusa and Col. Robert Parker both fit in there somewhere too.
When Berlyn (WCW mainstay Alex Wright, repackaged) debuted, he originally came out accompanied by three bodyguards and a pretty female interpreter named Uta who was getting surprisingly popular fairly quickly. Then Uta and two of the bodyguards disappeared about a month into the character's run with absolutely no acknowledgement.
In late 2010, after his Face–Heel Turn, Tyson Kidd appeared on RAW with a new bodyguard, 7-foot developmental talent Jackson Andrews. Andrews, for all of his size and intimidation, was as green as grass, and after about 4 weeks, following Kidd losing a match to Mark Henry, Andrews sustained a World's Strongest Slam from Henry and returned to developmental limbo, where he would be released soon after, never to be mentioned or talked about again.
Happens a lot with valets, for instance, Carlito's temporary bodyguard-or-something, Jesús (as in "Hey-suess"), who, in Kayfabe, stabbed John Cena in a night club. He then faced Cena in a street fight at a PPV, which resulted in Jesús getting beaten within an inch of his life and never being mentioned afterwards.
If not for CM Punk's throwaway lamentations, those who don't check WWE corporate statements would probably be ignorant about guys like Festus/Luke Gallows, Mike Knox and Vladimir Kozlov getting 'future endeavored'. Nor would they be aware of John Morrison, Melina Perez, Gail Kim or the Bella Twins just up and leaving.
Or, in the case, of the Bellas, returning out of nowhere either.
Possibly justified example in Chris Benoit after it was discovered he had killed his wife and son before committing suicide. DVDs prominently featuring him were discontinued (some permanently, such as his biographical release), commentary for certain matches featuring him were edited, and his name was removed from many pages on WWE's website. As of late, they've steadily begun reversing this course, but never so far as to even indirectly mention him on TV.
Remember the guy who won Tough Enough? Andy Leavine? A few videos aired for hyping him up, however they stopped and he was quietly released months later, never to be mentioned again.
Since walking out in January 2014, CM Punk has become one of these. His first mention on WWE television since then was the March 2014 episode of Raw where Paul Heyman came out to his music. Later on, however, at Payback 2014 when the crowd was chanting Punk's name, Stephanie McMahon told Daniel Bryan, who was in the ring with her, that they wanted Bryan to quit as CM Punk had.
Kozo Urita aka Tiger Shark, a Japanese professional wrestler and Mixed Martial Arts fighter known as part of Satoru Sayama's entourage, was a mainstay on Real Japan Pro Wrestling from its foundation year until October 2013, moment in which he vanished for no explanation.
A similar example is Hisamaru Tajima, who was set to become the ace of Toryumon X. However, after only two matches in Mexico, he disappeared completely, and Taiji Ishimori took his role as the next Toryumon ace. The reasons behind his exit are unknown, and the only information about him after it is that he opened a restaurant in Nakano, Tokyo. From 2006 to 2012, Tajima returned to pro wrestling, popping up in several promotions and becoming a regular in Dradition, before he disappeared again.
This seems to be recurrent in post-Dragon Gate Toryumon aces, as Hiromi Horiguchi, the ace of the last Mexico class, faded in the darkness as well in 2009.
Adam Rose had a guy in a bunny costume accompany him to the ring, and eventually The Bunny became a full-fledged wrestler who began to steal the spotlight from Rose, forming a mini-feud. When Justin Gabriel (the guy in the costume) quit, nobody replaced him and The Bunny disappeared without explanation. It was rumored that the man behind The Bunny would be Darren Young when he returned from injury to feud with former tag partner Titus O Neil (the two instead reunited and won the Tag Team Championship within 6 months of Gabriel's departure). Gabriel said in an interview that he had many ideas for The Bunny character, including a gritty character who would eventually turn out to be Vince McMahon, but most of these ideas were shot down by Triple H.
The WCW Stable the Dungeon Of Doom saw many departures. Some simply left by turning face, but One Man Gang, Maxx, and The Master all disappeared from the company without any explanation.