Arma 2 - unowned?

So, I was browsing the steam store, and came across Arma 2, it wasn't displaying it as in my library, and I could have sworn I bought it during this last sale, so I checked my library, and it is there...but for whatever reason steam store is listing it as unowned. This is the only game I bought during this last sale, that's showing up this way....

Any idea why this is doing that?