My coolant light came on at 35k today. Took it in and after their tests, turns out I have a leak (I think he said thermostat but will confirm when I get it back) but said it was significant enough that he didn't recommend I drive it until the part comes in. So rental until I pick it up tomorrow.
Interestingly, my coolant light has come on twice (15k and 25k, both 5k after the service interval) and they tested both times and said no leak. Today they told me that there was significant "crust" around the leak and probably why it was a slow leak and/or didn't show up. I check the oil and coolant regularly so I was watching it get to minimum thinking there is no way this car consumes that much coolant without a leak.
Being fixed under warranty. Glad the drivetrain is 5 years!