If the postmaster did not turn in your dispute and you did not turn it in to the NRLCA District rep, you are SOL.
The MOU on the dispute process requires a decision to be made on all disputes within 30 days of the deadline, which I believe was April 24 (don't quote me; the NRLCA website is down at the moment, so I can't double check that date). If you haven't heard anything by May 24, contact your union rep to find out the disposition.
In my district (and I assume nation-wide) there are relatively few disputes now so there shouldn't be any delays, and carriers should receive responses fairly soon after the deadline.