If you can prove that the company interfered with your ability to apply for the FMLA leave, you can get a court to prevent them from denying you the leave.  You should write a letter to the company today, saying that you are still waiting for the form;  send it certified mail with return receipt requested.

Should you have any problem going back to work, you need to take your copy of that letter to a good lawyer, who should be able to set the company straight.