It looks like it desiccated. I would cut it off until I found healthy stem and try again.

I would only let the wound dry for a week or so with rooting hormone, and then I would plant it.

Where are you located in Texas? I notice Live Oak leaves - that reminds me of my yard in Galveston, TX.

Jed, you put the hormon on and then let dry a week or put the hormon on right before being planted?

Cut/hormone/dry/plant

Create a hole in the pot or ground before planting because you don't want to rub hormone off. Also, I'd moisten the soil before you plant it, and then not again until you see leaves. I would recommend planting it in the ground now because it's getting warm, but you should be careful of getting too much moisture and we have a lot of that coming to Texas.

This time of year I like to root them in full sun. They seem to take faster.

Looks more like a severe sunburn than a rot issue, judging from the images.

I was thinking sunburn too.