Most states have procedures for handling small amounts such as a final paycheck, but before you do that, see if the employer won't re-issue the check to you. If indeed there is ONLY the one check you need to cash, this would be the easiest process.
Absent that, there may be an affidavit procedure for you to follow claiming the money particularly if you have paid for or committed to funeral or other last expenses. Again, this is only true if there are not other probate assets to be passed.
In short, please consult with a local attorney to determine exactly how to do this most economically, and in keeping with appropriate law. Good luck.