after so many hours there are huge possibilities that he did not eat that mushroom or the mushroom was not lethal or highly toxic. I have read a story of a poor piggie who ate a very little piece of a toxic leaf and after 1-2 hours he started being ill and the vet couldn't do anything.
There are luckily only very few lethal and higly toxic mushrooms (Amanita Falloide for example) which damage the liver and nothing can be done; then there are a lot of mushrooms which can cause troubles, but not the death. I don't think that little mushroom was lethal... Try to make a research online, try to look for the name of the mushroom, so that you can relax...

My father was a mychologist, I have never learnt to know mushrooms, but I remember when he used to show me the very few species which send a human to the heaven... they were not the little ones we find on a lawn...[/QUOTE
with us humans sometimes doctors use medicines which make us vomit the toxic food, but piggies don't have the reflex of vomit...
thank you so so much , I have been watching him like a hawk for the past couple of hours worrying myself , I ALWAYS check for mushrooms on the lawn and was so panicked when I saw that I hadn't done it properly , thank you so much for all of your help