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Yeah, but that’s only really a trap is there’s a way to keep him from escaping. Voldemort escaped pretty easily; had Harry not been there, he could’ve tried for some time, figured out the trick and then just left to re-evaluate his options.
While not explicitly stated, it’s possible that that’s actually what he did: If he’d figured out Harry, Ron and Hermione had been snooping around and had found the room with Fluffy, Quirrel might’ve willingly dropped hints so that they’d check, let the music play longer than he needed to so that they’d know someone was trying to take the stone and he could lure them all the way down.
Are you a wombat?