Certainly this situation could cause stress-induced diarrhea, and can be attempted to clear up at home as long as they are acting normally otherwise, non-painful, and still eating. If it doesn't clear up at home, then a vet appointment is necessary, as antibiotics or just something to settle the GI tract may be needed.
For now, don't feed anything for 12 hours, but do allow water if he'll drink. (If not, he can always have some unflavored pedialyte). Then when you do feed, give a bland diet like baby food (chicken or turkey flavors) or boiled chicken. No treats, and don't let him eat grass either. Continue this diet for a couple of days as the stool firms up. Once firmed up, gradually go back to the regular diet over the course of a few meals. Keep your kitty indoors while recuperating if it is at all possible.
I wouldn't worry for now if he's acting fine, try this, and if not clearing up in a couple of days, you'll want to make a vet appointment then.
Best of luck, and let me know if I can help further.
Christine
Certified Veterinary Technician
Licensed veterinary technician (B.S. Mercy College), 10 yrs in animal medicine and training