She sounds like a trouble maker. He may not even have gone over there on Wed at all. He may have been telling the truth about just waiting at the dr. You won't know til you ask him. Try not to get angry til you find out his side. He may have just popped in straight from work, then gone to the dr. It may be a non event. Or it may not have happened at all.
Talk to him as calmly as possible and hopefully its nothing to worry about.