You done the right thing by looking for her owner but it`s not had the outcome you wished for sadly. In this case it may have been better to let the cat decide, but then she may have had a frantic owner searching for her so you wouldn`t have known either way. If she`s got out before, she may do so again and chances are, she will follow her nose and come back to you and if she does, I wouldn`t say anything.
But wait and see if that happens. x