My experience is that not all owners want their bird back. some would just open the cage and let them go because they don't want them anymore... Too much work, noise, trouble when you want to travel and have no one to take care of them. Happens a lot before the Summer around here I'd say if this bird has been in your care for 2 weeks and no one has answered your ads neither tried to put up flyers/ask on FB, then it sounds like that bird was not welcome where he comes from and is much better off with you..