Had it checked with me watching like a Hawk. Went through all possible scenarios. Checked Coolant for oil, plugs for fouling, pulled the MAF and Filter to check the inside of the intake, had the guy do a compression test, as well as pull the injector/fuel rail to see if there were any shenanigans happening in the valve train..... nothing.
It's as good as new. My mechanic isn't sure were it went, but considering track days, and a longer than usual oil change interval.... 4 mo's, he's not really sure that I should be worried. It hasn't lost "ANY" oil since, is running like new, and has no obvious problems.
I also talked to another GM service mechanic, and heard a similar story, that several of the LS2 powered cars (Trailblazer, Vette, Escalade) on some oil changes would come in very low on oil. If relying on the Oil service indicator, many would be low up to 3 quarts by the time they bring them in. His response/diagnosis, as well as GM official stand on the issue is that during engine braking, a tremendous amount of oil finds its way into the chamber because of the vacuum created by the pistons leaving TDC without a big burn.
So far, with no more engine braking, I've lost no oil. What he said... seems to make sense, though I never know with service guys.