If he remote started it, it will shut off after 10 minutes. It can be remote started twice before it will be required to start with the key.
Depending on engine and r.p.o. codes, if it cranked and no start until the battery died, I'd look at the underhood fuse block for any corrosion or critters, and then if it has one, the fuel pump control module and the fuel pump.
Fuel pump/supply is about the only thing on those where they will crank until dead and not set a single dtc.
Edit, this is assuming it's a 6.0 gasser as I don't see a Duramax emblem.