That used to happen quite a bit when I had a full house and could not always keep track of all My Found Cats ^^.
They used to hide in the most unlikley spots , in the crawl spaces in the cellar, in the cupboards , or in the oddest places.
I am glad that you found Buddy , and let him loose.
I wonder if he will ckalk that up to a bad memory and never go into the closet again.