I've had that happen twice, once on the old A340-500 and once on the 777 new F.

There are worse situations to be in, although I won't deny I do feel a bit sorry for the crew member who has to sit around for hours with nothing to do while I'm asleep.

On my penultimate in new F, I was completely unaware that there was another pax in the F cabin until we arrived at DXB off-stand and took a throne bus to the terminal. I was in 1A, he was in 2K.