anyone located/killed this thing? heard rumors and bets months ago,..any luck?

There is no lvl 99 White Chocobo in FFXII. There is a lvl 99 Red Chocobo on Ozmone Plain, though. There's like less than 1% chance of encountering it after killing at least six chocobos on Ozmone Plain after you've received the Treaty Blade. I haven't seen one myself. ^^