If it appears to be clean, it's probably fine, and I don't think I've ever had something in a cabinet that was obviously soiled. But, it's not hard to imagine it happening if a prior guest put something up there by mistake.
That's not the same as I assume it is "sanitary." I understand that the dishwasher is probably not capable of sanitizing dishes the way any commercial kitchen might. It just means I am not worried about whatever might or might not be there.