I dont know what you look like so I dont know your situation exactly....but sometimes i fyou lose alot of weight you have some loose, stretched skin that may appear to be fat but isnt.
More than likely though, you just have a "problem" area...like myself...and need to get VERY VERY lean before that area tightens up....my abs usually come in 1-2 weeks before a show and not a day sooner.....just how my body works....genetics suck somethimes.
Try increasing your fiber intake from green veggies and maybe some psyllium in your protein shake and see if that helps as well.