I made a deposit at a schoolsfirst?

it was a third party ck. they notified my bank in four days my bank rejected the deposit. it has been twelve days and my bank still does not have the ck. said they are waiting for fscu. to return the ck. to them why are they taking so long to return the ck. i needthr ck. so i can cash it. i dont know when sfcu took over this atm but i will never do business with them again if you can notify the bank in four days about it being a third party ck. why can,t they return the ck.? this has really put a hardship on me. i have deposited third party cks. at this atm and never had a problem. a third party ck is a third party ck. i really need to look into this legally. thank you for ananswer laura