If a company pays out severance to other employees and you find youself in the same situation...

I work for a wireless communications company based out of California, but I am employed in a retail store in Oklahoma. Back in 2009 they closed a store in Pryor, Ok and offered everyone positions in Tulsa, Ok approx 45 miles away. Under the company policy of severance, "if you are offered a position within 60miles of your current position, the company will not pay out any severance." However, they did pay it out to all employees who declined the job offer. Now they are closing our store, but they said there is not to be any severance paid out. I mentioned the Pryor, Ok store and about them getting severance. They simply said the policy has now changed to "if you are offered a position elsewhere, there is no severance to be paid." They cannot tell me when this policy was changed, nor can I find the policy change anywhere in the HR department. Would precedence come into play here since they did offer severance to another store? Am I bound by this new policy even though it was never posted nor were we informed of this change? Is there anything at all I can do to get my severance pay? Thanks for your time and help in this matter. Many blessings!