Jimmy intentionality left the rocket for Sheen
The Yolkians will appear in a future episodeJossed.
Sheen has been gone less than an hour earth timeSo his parents and friends didn't even realize Sheen's absence. After all, that wreck of a show only lasted for one season.
Sheen comes back to earth someday.Confirmed. An episode of The Adventures of Jimmy Neutron (The Tomorrow Boys) features a future Sheen working as a famous male model. This explains that Sheen did indeed return to earth. If he wasn't able to repair that rocket he crashed, then Jimmy must have picked him up. Either way, Dorkus must be so pleased that the bane of his existence has left.