My new unit says I don't qualify for the Overseas Service Ribbon awarded to me by my previous unit. Are they right?

I deployed to Afghanistan in 2012 with Temporary Change of Station (TCS) orders that said my tour would be no longer than 270 days (about 9 months). My tour ended up being 8 months and 1 day, as my unit redeployed a few weeks early. The unit I deployed with awarded me the Overseas Service Ribbon (OSR) for having completed a tour. I arrived at my current unit a few months ago, and prior to my recent appearance at the promotion board, S1 reviewed my records and removed the OSR from my ERB, stating that I didn't serve overseas long enough to qualify for the OSR. My Platoon Sergeant is the one who made me aware of S1's decision to remove my OSR, and he hasn't disagreed with S1's decision or made any moves to investigate the situation, so I did the research on my own.

AR 600-8-22 says that the OSR is awarded to Soldiers who are credited with a normal overseas tour completion according to AR 614-30. AR 614-30 says that a Soldier has completed a tour if he serves to within 60 days of the prescribed tour. I was deployed to within 21 days of my prescribed tour, and my early return wasn't under my control or by my request; my whole unit redeployed a few weeks early. According to my research, I should be able to keep my OSR.

I'm going to print my TCS deployment orders and take them to S1 to show that my prescribed tour was only 9 months, but beyond that, I haven't decided what to do. Has anyone else been in this situation, or can anyone explain where I went wrong in my evaluation? What would you do in my situation?