I think a long time ago, the system DID save up all the redeemed rewards and WOULD give you an enormous amount when you finally did get on the game… That would have been back in FM3~FM4~FH1 timeframe… It does not work that way anymore; now, when you redeem rewards, you had better get on the game and make sure you actually got them, and do it quick. I’m not sure when things changed, or if I’m just crazy and nothing has changed (but I feel confident this change did indeed occur), but man does it suck.
As for the loyalty rewards (cars, money just for having done whatever in the other games), I have no idea what might have happened. You and your friend do have separate XBL accounts, right? There isn’t some way that he could’ve gotten your rewards by mistake, is there…?