Well, if it was open like that, then its quite possible that the cat did. Wouldn't take much at all to get it. Cats tend to do that. lol Our old cat had chased my hamster once when he got out of his ball. Luckily he was under my desk and I saw him chase him out of my room, so I snagged the cat before he reached him. xP;;

It was really sad. She wasn't very social, but she was the prettiest hamster I had ever seen. And she was still young and I hadn't had her long, so she hadn't had the time to adjust.