Can my union negotiate away money already owed to me?

My school district had a terminal pay program for employees for which I qualified. In 2003-04 the program ended and balances owed were to be paid out via a "Longevity Pay" program with yearly payments by formula. In a new contract the "Longevity Pay" program was to be phased out and anyone who retired would receive their balances. I was not eligible for retirement and had a balance-which the union said the district could confiscate. There was no clear language in the contract about forfeiture of personal funds-so I filed a grievance. The union fought me on filing and it came out during discussion that it was my union that proposed the clause (as a way to encourage senior staff to retire thus saving the district funds). I eventually was able to file and my grievance was denied. I eventually had to appeal to the MEA and they denied my claim. Do I have any recourse to recover my termination/longevity balance?