Many years ago when I was a teenager, a neighbour of ours found a hamster in her garage. We asked around the neighbourhood, put notices up in the newsagents, even called the local police, but no one ever admitted to having lost it.
It was a golden hamster, apparently fully grown, and in fine health. Our neighbour gave it to us as we already had hamsters (2 dwarves at that time, leaving us with a spare cage which was suitable for a syrian). When no-one claimed him, we named him Hannibal and he lived for two more years very happily in the kitchen with my mum feeding him raisins every time she baked
We never did find out where he came from but he was a tame, happy, healthy boy and I'm glad he found us.