On Seascape in October one person was laying on the sun bed next to me. When the waiter asked if she wanted a drink she asked if she had to be a YC member. She said she was not one. The waiter walked off and about 30 minutes later she decided to leave on her own.
Last week on Meraviglia someone wandered into the pool deck and asked where the slide was.
So yes, it happens often. These are only two examples, I have experienced and seen more.