Hey man, I would love to help you, but I need a bit more info from YOU before I can.
Where did you find it? A damp, cold corner perhaps? Temperature, condition, surroundings of where you did finally find him helps a lot.
How long ago did you find him; how long has he been back in his cage?
Describe your cage, and how he escaped in the first place. Also, the temperature and conditions of the cage would be helpful.
Finally, how long have you kept this guy, and how old and how big is he? How often does he usually eat?
Once these questions are answered, most experienced keepers in this forum can give you a lot of good advice.
Without knowing any of these particulars, I am tempted to say that he is fine, but stressed, and that you should let him settle back into his cage for a week before offering him any food, or you could make the situation worse by stressing him further. If the "diarrhea" you are afraid of is just a smear, perhaps in/on/or around his water bowl, it may not be anything unusual. However, if the "diarrhea" is in fact a lump of jelly-like goo I would rush him to the vet. The details of your observations are critical here. Like I said, you need to give some more information before you expect to get any really useful advice.
Cheers,
~Rebecca
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0.1 Dumeril's Boa '04 (Courtney)
0.2 American Pit Bull Terriers (40lb darling lap dogs:Brandy&Mara)
1.2 Ball Pythons
[1.0 '05 Orange Hypo (Specter)]
[0.1 '05 Het Hypo (Sylvia)]
[0.1 '03 Normal (Sue)]