Take a deep breath and don't give up. Chances are they will eventually find your bag. I've gotten a bag back about 1 month after returning from a trip once. In the meantime you can estimate the cost of the bag and your possessions in it. This is pretty standard for any customer/airline claim. Furthermore items you had to buy during your trip you should have all the receipts to also submit for reimbursement.
AA has been pretty good about this in the past. Iberia for example hasn't. Good luck.