Good to hear you have hedgehog signs there. The poo in the doorway of the hog house probably means, at the very least that a hedgehog has been in to investigate. It may still be in there, or may have done the poo on the way out. They do sometimes go in, just out of curiosity or sometimes the hogs here go into the boxes for a nap and then go on their way again. You could try putting a very thin twig across the entrance so that it broke easily if they went in or out. Where the twig ends up may indicate which way the hog went, but you still wouldn’t be sure whether it went the other way again afterwards!
Unless you are able to watch the hog house, from a distance, you may have to be content with the knowledge that the hog is around and has shown interest in the hog house. Hopefully you’ll see it soon, one way or the other. Good luck.