If you find a hedgehog in the daytime there is usually something wrong with it.
It needs to be taken in to care immediately. It will probably be dehydrated and often a victim of fly strike. This is where flies realize the hog is dying and will lay their eggs on it, usually behind the ears and along the skirt as well as between the spines. You can identify this problem easily by observing the hedgehog looking for small clusters of white sausage shaped eggs. These need to be removed immediately as they hatch into maggots within 24hrs. Keep the animal warm and offer meaty cat food and water then take to your local wildlife centre or hedgehog carer.
There is a golden rule with hedgehogs. If it can happen to any animal it will happen to hedgehog. They find themselves in all kinds of situations. They get court up in garden netting, trapped between sheds, fall into garden ponds, and get stuck down drains and even severed by garden strimmers. They get attacked by other animals, hit by cars, fall into cattle grids and poisoned. The main thing is if you find a hedgehog that's in distress get it to someone who knows ASAP. Other problems for hedgehogs are lung worm or other internal and external parasites, such as a heavy flea or tick burden.