Depending on what part of the Med you were going to, its possible that an augemented crew was used, therefore even if the captain was in the cabin, there could be 2 others in the cockpit, or that captain could be a check airman in the jumpseat and the normal crew were still in the cockpit, or that captain could be jumpseating home and the normal crew were still in the cockpit.....
Lots of reasons why a captain could be in the cabin, so dont panic
Mutt