EDIT: Shortly after posting this, my xbox decided to pop the achievement whilst I was at the dashboard, crying (jokes). Seems like I had a major case of achievement lag.

I know this game is old now so I'll be thankful if someone can help me out.
I finished the game with one bounty card to collect. So I loaded the checkpoint, collected it and the game saved - no achievement. Now it won't even show up in my inventory, however if I try and collect it again the game says I have already done so (so it doesn't unlock it in the inventory).
I have tried a number of things to correct this - including redownloading my xbox profile. Nothing has worked.
Googling the issue has not proved helpful.
Anyone have any ideas?
Its an achievement worth 30 points and is annoying to do, I don't want to throw away the work I did for it.