I would never had let a Uro roam the yard, even on any type of harness. Eating the grass, probably not the best thing for him. Anything they eat should be free of pesticides, herbicides, fertilizer 100%. Not to mention the temperatures a Uro needs, it would need to be really really hot and dry out to bring him out.

Hopefully everything is fine, my only suggestion would be to get a fecal done to see if there are any parasites from eating things outside. Just keep your eye on him and make sure he gets the proper diet.