As mentioned, most new trucks wired from factory with 7-pin connector, and integrated trailer brake have an ignition switched isolator to prevent the trailer connected load to drain battery in the tow vehicle. Aftermarket wired TVs should have an isolator installed in the power connection (pin at 1 o'clock position, looking into tow vehicle socket) Link here
Test the TV pin connection with a test light or Digital Volt-Ohm meter with the ignition switch on and off. That should confirm.
IF it is isolated, then something was left on in the truck, draining the battery.
Hope this helps,