The first storyline of A Modest Destiny had Maxim pull this from time to time. However, he took it to the next level by substituting an "escape dummy" (a giant stuffed doll of himself on a scarecrow frame) before running off.
In El Goonish Shive, characters distract each other with some variant of "Hey, is that a demonic duck of some sort?" It always is. (except for once there was a picket sign instead, stating that the demonic duck was on strike. This caused the distraction to fail.) Occasionally he complains about feeling used.
In thisNodwick strip, Nodwick, Yeagar, and Artax have lured a giant demon towards a lake full of holy water that they are standing in front of. Artax yells this warning to him, and the guy says, "Sorry magic boy, you're going to have to come up with something slightly more original. Telling me my shoelace is untied won't work either." Unfortunately for him, Artax isn't bluffing; Piffany, who is piloting an angel-shaped Humongous Mecha, does a cannonball into the lake, dousing him and melting him into sludge.
A strip in Venus Envy uses a literal variant on this that actually works: "Gah! Lookout! A distraction!"
That's actually a running gag in Venus envy. It showed up in other webcomics too.
San Three Kingdoms Comic, a Romance of the Three Kingdoms webcomic, has a Running Gag of avoiding discussions by pointing behind and yelling "LOOK! BAOZI FAIRY!!" then the pointer escape as people try to look for it. It's currently an unused gag, it either fails or must use a variation to pull it off. (Using "Baozi" on Zhang Fei won't work. Use 'Wine', however...)
Legendary Frog used it in his Resident Evil flash cartoon, only Brad doesn't even wait to see if they look, he just runs like hell.
And let us not forget how Zeromus (the representation of Alex's hatred) was tricked into turning around three times. Naturally, the moment he finally catches on and refuses to look, the thing Bob and Alex are talking about (a naked Alanis Morisette, the representation of Alex's cynicism) actually is behind him.
In General Protection Fault, as Nick and Fooker break into Trent's house for the evidence that he's behind the safe droppings, he finds them and aims a shotgun at them with one hand while holding the evidence with another. They distract him by telling him Steve Forbes is behind him before taking the evidence and escaping.