Houdini has been foiled once again, thanks to the Early Warning Kitty System (Copper, yowling up a storm, which she never does at night. Ellie will do a round of the "It's three a.m. and I'm alone and hate it" chorus occasionally, but not Copper). Even though we've been closing the office up at night after the last few incidents, I decided to go check on Lucy, and the little bugger wasn't in her cage.
Luckily, despite the fact that she probably could fit under the door (Jeff says hamsters can scrunch pretty good), she was still in the office (so why was Copper yowling? Concidence, change in smells in the house?) We chased her around for a few minutes and finally got her back in her cage. We traced the problem back to a door on a space needle-like attachment on the cage. It was ajar. We're not sure if Jeff left it ajar earlier or if she popped it open, but there's a heavy measuring tape hanging off of it as a temporary fix (the other doors are twist-tied or otherwise pinned shut.) Whether or not she opened it, Lucy definitely expected the door to still be ajar - we just watched her try to get back out again, be unsuccessful, and get very pissed.