Coolant level low warning

[cravin]

This morning I was leaving the house and the engine coolant level warning popped up on my HUD. I drove to the gas station and opened up the reservoir expecting to see some fluid around the min level. To my surprise the reservoir was almost completely empty and took half a gallon of Peak. There was some white crust around the reservoir knob.

I don't have any coolant on my driveway. Any clues as to what else may have happened? I'm guessing that they didn't fill it during the CPO flip, and it's not one of those things that I just check regularly.