Update:
Well, by the time I got dressed, Miko was out cold, sleeping finally. I talked to a woman that worked there, we both agreed to let him sleep and see what happens later in the day. He finally woke up about an hour ago, walked around a bit, but no pooping, and then he went back to sleep. He's been off/on sleeping so I have been keeping an eye on him.
The woman I spoke to just now, talked to the vet earlier, to make sure we're all on the same page. I'm going to give him some food and see what happens. If it upsets his stomach, I'm going to the vet this afternoon. Surprisingly, they're not overly concerned with his diarrhea being reddish brown.
On the upside, they have been nothing but wonderful. Keeping me up to date on if the vet can see him during an appointment or if I'd have to admit him (vet had surgeries today, no appts, but two were cancelled so they called).
I still have yet to figure out what could have upset his stomach. I haven't started anything new last night. The only new thing started a few days ago and you'd think you'd see a faster reaction.
I'll keep you posted after he gets some food in him. That will tell us how irritated his stomach is or isn't. Otherwise, he's just exhausted. He was up from about 2-7am and that's rare for him to be up that long.