A day earlier me and my friends went to one of their houses and recovered our gamertags fine. The next day we went to my house and one of my friends achievements were all gone. I checked on xbox.com and he still has no achievements. Even after earning an achievement while online at my house, we checked it right after and he didnt get the achievement it said he got.
The only reason I can think of that this could have happened is an xbox update on my friends system the day before that we refused. Me and the missing-achievements friend recovered our accounts at that house, but I have all of my achievements still.
I feel guilty that he lost his achievements at my house so how can he get the achievements back?