SegaXtreme

Just an odd remark/question maybe. I got some master system games in a lot and one of them is Altered Beast (according to the case and the cartridge label) but it is actually Missle Defense 3D. Seeing as theres no way to see if a master system cartridge was opened, did this happen a lot? People would rent games and maybe switch the insides just to have the new game? There wouldnt be much of a chance of this coming from the factory like this I assume.