He probably had to go really bad. Haven't you ever had to pee in the middle of the night? If its a one time deal, don't worry about it. Clean it up with an enzyme cleaner and see if tonight is a repeat performance. If not, then no worries.

I let Nicki out around dinner time, and again just before bed (usually around 10:30) She gets let out again at 6:30 in the morning when hubby gets up for work.