Hi cox05
The most important thing which rings alarm bells is a hog being out during the day – especially as it stayed still and then moved very slowly. If you see one like that again, the best thing to do is to ring BHPS to find the contact details of your nearest carers/rehabilitators and take their advice.
If you’re worried you could pop the hog into a box (with either torn up paper or a small towel which the hog can bury in, with some food and water) whilst you are getting those contact details.
Apart from that, yes setting up a camera sounds a good idea. Then if you are sure that isn’t being used by a hog you could go ahead with your shed replacement. But yes, under sheds are quite good places for hogs to build nests – and nice and dry.
Good luck.