Given as though I see that you are relatively new (job level wise etc). Have you followed all the proper steps to attempt to leave the FC? aka going to Free Company via Start > Free Company and then selected (I think it's the members portion of the screen that gives the option to leave?). If I'm not mistaken, when you leave the FC it will auto demolish your room and all your items will go to the Caretaker NPC in the residential area same with your chocobo (if he/she is stabled when you leave).

You can also try to type in on a search engine regarding your issue and you may find someone may have had a similar issue, but it could have been user error in not taking the appropriate steps to actually quit the FC.

Not trying to sound like an ass, just trying to help.