DUnta, why do you need to be on the crewlist? THey are already on the ship, so being added to the crewlist won't make any difference - they can still move around without having 'access'.
Being assigned will help, just be letting you know where you are so you can let someone else know where to pick you up from.
Anyway, send a DM to the person/faction that owns the ship if you went inactive while on there. Then try posting in the Traders Lounge and see if anyone knows the owner of the ship you are in. THen it will be a matter of being assigned so you can fly around, or getting the location so someone can come and pick you up.