K.B.
My son peed his pants two times the other night. Very strange for him. I'm kinda strict about the whole thing. The first time, I couldn't tell exactly HOW his pants got wet so I just said "You know how to use the potty and if this is pee and you do it again you will be in big trouble" and he just said "O, I know Mommy it's ok. Just say it, just say it happens" The second time, in the same night, I was done. I made him take off his own wet clothes, gave him a shower just long enough to soap up, wash his hair and out, and then he sat in time out. He was still crying when time out was over (which he started as soon as he had peed cause he knew he was in trouble), so he went to his room and calmed himself down. We haven't had any trouble since then, so all is good I guess...at least for now.
I honestly think by this time, if they were completely potty trained already, then they shouldn't have trouble making it to the bathroom. Once you find out if everything is ok with him health wise, then I would start with punishment when wet/rewards for staying dry.