huh
How exactly does that work... DOA doesn't exactly have saves, Besides Saves are embedded within the profiles so that would be a difficult trick to pull.
If you play 2 player though using a profile with a lot of achievements, quite often it will bestow your achievements on whoever beats you... My brother created a profile and we were playing some 2 player, we played about 8 or 10 matches in a row which I won. then he won and it gave him an "Achievement Unlocked Message" clicking the guide button it showed he's unlocked all of my story mode and played for X hours achievements

Not only that but I've heard of this exact same thing happening to several other people.