Just to add something a lot more trivial to the hard stuff Dinwar said, I hope people realize that most of the history of the human species has been before the last ice age. The majority those flint arrow heads and whatnot are from before the end of the last ice age. The glaciers didn't destroy those. As are a buttload of skeletons and skulls, some showing signs of healing after wounds, and some still having arrow heads embedded in them.
Yet we have none that show any advanced surgery done on them, nor any from before 1000 BC or so that have iron arrow heads in them.
I suppose one could conceive a civilization that was INCREDIBLY good at removing all such traces, including removing all arrows and whatnot after a battle... many of which they would have
lost, and destroying all pieces of advanced pottery, and finding and destroying all skeletons, etc. But it's kind of a conspiracy theory, innit? Nobody in practice is THAT perfect at keeping a secret, especially when they have no reason to.
Also I think people overestimate what the ice age meant. It was NOT the Pixar version where everything is ice, as far as the eye can see. Actually, it's just a bit colder. This means you have arctic weather a bit south of where it is now, but down south you just get some snow.
Basically there is a reason why the last glaciation created fjords in Scandinavia, but not in Italy. There were solid ice sheets down to around 45 degrees north latitude, but south of that, there weren't. For reference, that's about the latitude of the southern end of Austria. A civilization around the Mediterranean (so it can then get drowned) or central America would NOT be covered in miles of ice. It would still get warm enough each spring for the snow to melt off.
And sure, the sea level did drop by some 110m (some 350 ft or so) during the ice age, but that is actually a rather narrow band of new shore. There is no sane reason to assume that a civilization would be concentrated only in that narrow band, and absolutely shun hunting inland.
Plus, that difference in water level existed only during the glaciation, and got that extreme only by the end of it. I.e., such a strange civilization concentrated only along the shore line would have to have existed only around 15,000-10,000 BCE. Something from BEFORE the ice age would still have the same water line as today. It'll only be under water if it was underwater in the first place.
I.e., if it's R'lyeh or something