Good, a little less risk then. You can salt his hay to get him to drink more and maybe exercise him a bit.
I had a fellow boarder's horse get out and happily munch half a bag of Omolene......he was longed and just wouldn't quit running
, which is not normal for him. He came out of it just fine.
Watch him today, maybe, as suggested, a "just in case" call to the vet for opinion might be a good idea.