I'm confused by those of you who are saying that, since the mother willingly let the presumptive (but not technically proven) father see the child, he's under no obligation to return the child, absent a court order.
Since he hasn't been proved to be the father, then technically he has no more legal right to keep the child from the mother than, say, a grandparent, aunt, uncle, or a friend. What would happen if my daughter let me take her baby on an outing for the day and then when she came to pick her up, I just said nope, sorry, I'm keeping her? Would you say then that, because my daughter willingly allowed me to see and spend time with the baby, that I was under no obligation to return her when the time came? Would she have to get a court order just to get her child back from me, because she willingly allowed me to spend time with the child?
I understand that it's not up to police officers to determine the parentage of a child, but if someone asked for the help of the police in getting their child back from anyone, no matter who that might be, wouldn't the police at least have the ability to look into the situation to determine what might be going on? Would they not be able to tell the presumptive father that if he agreed to return the child at a certain time then he should do so? If he refused, then clearly there would have to be some sort of court order in hand, but absent that at the moment, why does the presumptive father seem to hold all the cards in the situation simply because the mother willingly let him take the child?