I've had this happen a few times, mentioned it to the dealer when I took it in for other stuff but they could never duplicate it & it does not store any codes (I just wanted it noted that I'm having occasional issues).
Here's the scenario. I use fob to unlock truck & start it with the key, Theft Deterrent msg pops up on DIC. Sometimes it will kill the engine on it's own, other times it stays running. In both cases I turn key off & remove it, unlock doors with fob, open & close doors, restart & everything is fine. It will also happen if I start the truck with the App, open door with FOB, the insert key. I don't feel comfortable driving with it on, as for all I know it could die at any moment.
Over the year & a half I've owned the truck it seems to act up more in colder weather (It's been happening a fair bit the past month or so) & also when I unlock the door & get it and start it relatively fast. The DIC always flashes different things on start-up (Bluetooth connected, Warning Ice on road etc), it's almost like the computer is not fast enough to process the info & throws the Theft Deterrent message.
So far it's been mainly a nuisance, but I had a similar issue with on a 2001 ZR2 that progressively got worse until it would finally prevent the truck from starting at all & that turned into a royal pain in the

. It's a well known issue, just Google "GM passlock problems".
I hope the same problem does not start to affect the 2nd Gen Twins down the road...
@GM Customer Service If I brought this issue up with my Dealer before my warranty expires & they cannot solve the issue, what happens when it becomes a bigger issue after my warranty expires?