Take her away with good intentions not to be seen again? Get real that's a crime! It's not a tricky situation. If you find a 3 year old under a bush you do the right thing and bring her to the authorities/creche/OC or call them/get help because she's not yours - you don't leave her there alone on a dark cold night.
The "good intentions" when a rescuer first finds her and picks her up. They are the intentions I'm exploring. Later e.g. the next day he might have second thoughts and I think you are confusing the two.
They might have second thoughts. For what explanation would the finder have for being there in the first place.
There is a classic ad in NZ where this person finds a piglet and discovers who owns it and as he is bringing it back to the right farm he reads the sign "Free Range Pork" and decides to keep the piglet for himself.
https://www.youtube.com/watch?v=_KTfyrTTey8 Can you see the connection to Madeleine McCann?
I see there is an Irish version too.
https://youtu.be/e2b_2-8GYyQIt is quite funny really.