Unfortunately it did, twice in the first month I had my first snake. Despite having screen clips, he still got out once. So I added more screen clips (had five on a 20 gal) and he got out a second time. He was then moved to a "snake proof" enclosure I built. I don't really feel like I "let" it happen considering I was doing everything I thought I was supposed to be doing with a single snake in a glass terrarium.