Well I'm glad that he's better, but hopefully he is less than his usual self only because he had the "24 flu" so to speak. If he isn't drinking enough, does he have a blue block out away from the other horses? Or maybe, put a few large chunks of blue block in his feed dish so some of the salt will get into his food and encourage him to drink more. Did he seem dehydrated to you? If at all, it takes A LOT of water to re-hydrate.
Still doesn't explain what happened, does it? Maybe you did prevent a full-blown colic. Hopefully he will pass a good night and drink some more in the morning just to be a good boy!