Forum:Please explain

Hi everyone. This is one of the strangest things I've had happen to me on Borderlands. I had a Maliwan whatever Fulgrating stinger that was worth 9999999 money, x4 shock, perfect parts and Level 61, top of my purple list... Ok, cool perfect SMG and all, but today when I looked through my inventory, it was replaced with a level 57 Lightning stinger (shock x3, still top of my purple list, worth 7.5 million). I'm not making this up, but I would like to know what voodoo magic is responsible for this occurrence. Does anybody have an explanation for this?