I am surprised your Realtor did not tell you they are waiting for a signature form the seller if that is the reason...I would ask to see a copy of the form immediately. This will tell you if they have both signatures. If they do then you can demand your check ASAP. If not then I would be insisting on them finding out why they told you something not true and report them to the Real Estate Commission.
If they have all the signatures and you just have not gotten it and do not think they have sent it then I would call or vist the office and ask to speak to the Broker In Charge. That person can help you out with getting your earnest money back ASAP. That person is in charge of the office and should be able to give you an honest answer and expedite a check for you.
Coldwell Banker United
Have you received a copy of the fully executed Termination? If so, I would contact either the Attorney or Firm holding such Escrow and ask when you might be able to pick up your check. If you have not received a copy of the fully executed Termination then you might need to start there.