2015 Yukon XL. Came out from church today and nothing... car wouldn't lock, unlock, no response whatsoever. Used the key to unlock the door and got in, still nothing. No sign of any electrical in the gauges/info screen (didn't notice interior lights). About 5 minutes later as we were getting into a friend's car to get a ride home, I hit lock button on the fob and the headlights flash and it is back to life. Get in, push the button, and it starts right up. Only thing that is out of the ordinary is the info screen giving an attempted break in notice (I assume from me getting in). When I got home I checked the battery in the fob and it was half into the green on my tester, but I changed it anyway. Anything else on the differential besides the fob being bad?

A bad battery connection would be plausible. Being in Houston, attempted theft is also plausible.

does your horn still work?

Didn't check horn at the time when nothing was happening. Now that it is working the horn does sound when I use the fob to lock. What would horn not working mean?

that someone probably tried to steal it (cutting the wires)

if it still works that's a good sign