We used to have a Staffordshire bull terrier that would bring home hedgehogs on a nightly basis from the surrounding fields. She wouldn’t hurt them, just herself in the process and she would leave them wherever we were.
i.e. if we were upstairs, so was her offerings.
As I have had some experience of hedgehogs climbing upstairs, it isn’t impossible that it came in through the back door when you weren’t looking and hid somewhere and then when all was quiet he came out and headed up your staircase.
As for droppings, hedgehogs tend to only poop shortly after they’ve eaten. If it had been locked in your house by accident and hadn’t had anything to eat, it wouldn’t have left you a present lol
