Haha, I did a similar thing just the other night!
I got home and was exhausted, so I fed my pets and went to bed. A few minutes after I turned out the light, I hear a "thump". Too lazy to turn on the light, I looked around and saw nothing. I went back to sleep. About an hour after that, I woke up to degu chirping... so this time I turned on the light, and found that I had left the cage door wide open!!!! And low and behold, I had a missing goo.. (at least the other two stayed in) It took me forever to find her because she didn't make any noise. I was worried that she might have injured herself, it's a long fall. I'm used to finding gerbils in the night scurrying around, they make quite a racket. Any ways, I woke up my brother, and it took the two of us 30 mins to find her, and another 45 mins to catch her and get her home. (it's hard to get small critters out from under dressers, especially when they don't want to move.) It was really weird tho, because the degu who likes to come out when I give them out of cage time (it's optional) stayed in, and the one who NEVER comes out, was the one who escaped ????