He doesn't look to happy about being back in diapers, if I was regressed I'd still use the bathroom even though diapers would be more convenient. I'd be way too embarrassed to poop in a diaper in front of everybody.
No choice but diapers...I guess he'll just have to get used to diapers for a while. Hopefully he can find someone to potty train him soon,or at least to change his diapers. At least he had diapers to wear before he lost control, the one thing more embarrassing than losing your potty training and using a diaper would be losing your potty training without diaper. Awesome pic by the way.