My house bun is sick. he's been free grazing for the last few mo the, staying outside most of the time, tho he'd come inside when he got the urge to.
we had a cold spell for a few days, and our first REAL snow. didn't see him out and about during the cold spell, so i assumed he'd burrowed in somewhere to keep warm.
it warmed up quite a bit yesterday, then rained all afternoon. I found Bun curled under a multiflora rose bush, soaked through and through
He's skin and bones! i brought him inside, and got him to drink a little and got a little warm mash in him (warm water, pellets, and a crushed tums)..... he was listless all day, cold to the touch, and whimpering.
he snuck off and found a hiding place last night. whn i still hadn't seen him by 2 this afternoon i was sure he'd found a place to die. BUT he resurfaced about an hour ago. he's moving a bit more, and nibbling on hay, but still very out of sorts. he also has very bad diarrhea

i really hope he pulls through this. he's such an awesome sweet bunny.
question is, what happened? he was fine last week.
perhaps he just didn't know how to find food in the snow? got chilled? do rabbits get pneumonia? or maybe he got worms? there are wild rabbits around.... could he have gotten some weird wild rabbit disease? he didn't have bloat or anything... just skin and bones...
any thoughts and suggestions to promote healing would be great. thank you!