I don't think that just cause she has no tags that her owner is more likely to be irresponsible....I don't actually have tags on mine right now (though I've been meaning to buy them) I love my pets more than anything...it's just they don't run away...and it's so small here anyway..

Anyway, seeing she is well fed it might be she got away?? I hope that is it and I hope she has nice owners who are worried about her and find her soon. It's really great you're helping her though, she could have been hit by a car or something Goodluck