No real theory on the why, but as far as I see it, LC could easily be undamaged. It was in the subbasement, which might be a bit sturdier and the whole lab might have survived. But that isn't the biggest clue to it. The biggest clue is, that Marcone built a friggin' castle on top of it. If Gard has figured out how to use LC, or if he has found other gifted individuals, he might use it to track down the Fomor's movements, or any other supernatural actions in Chicago. Or whatever the hell he can figure out to do with it. He is pretty intelligent in that regard, I think.