ive heard similar things.
just to make it clear to everyone else what im talking about:
Unique items with the same name do not drop more than once in the same game. ie. if u found a Bonesnap maul from meph in a game, u will absolutely not see another Bonesnap drop in that game again even if u wipe out everything in every location with 99999%mf. clear enuf?
this is my "evidence" for this fact:
theres an lod 1.09 mod (cant remember name) that allows awesome horadric cube recipes. u can mix a certain throwing potion with a scroll of identify and ull end up with elite uniques. i tried one of them and created a windforce. i used the same recipe again over and over and i got rare hydra bows everytime.
therefore uniques drop only once each game.
this does not apply to set items. meph once dropped 2 death's touch war swords at the same time.