Not exactly in the wild but a few years back a hunting buddy and myself were coming home from the deer lease.
We were driving on hwy154 between Quitman and Lake Fork about 4:00 in the afternoon
and one ran across the highway about 50 yards in front of us. There was one
other car on the road and it was in the opposite lane and had already went by where
the cat had crossed. It was fawn colored and had the long curled skinny tail.
It wasn't really running fast. More like a fast lope. The area it ran from and into was thick with trees.

I haven't seen one before but, 100% sure I heard one. I was frog hunting my uncles tank out by Decatur in the late 80's. The tank damm dropped down several stories to a creek below. Had my trusty daisy pellet gun and a flashlight slaying frogs. I was standing on the dam when I heard that sucker down in bottom. I will never forget that sound, and how fast I crossed the pasture back to the house.

Confirmed mountain lion deaths by the texas parks and wildlife map from 1983-2005
https://tpwd.texas.gov/publications/pwdpubs/media/pwd_br_w7000_0232.pdf

Twice, early 2000's I probably only 13-14. Denton County. Catching grasshoppers for fishing, looked up and she was walking across the clearing we were in. Saw her again about 5 years later. Was bass fishing that same creek and looked up, she was about 100 yards away, seated and just watching me. Humbling experiences

I have had the great fortune of seeing in Texas while hunting. One was near a small pond and the other crossed the road in front of me while on foot.

Used to work in seismic field and we would walk the woods everyday, a lot of places where man hasn't walked in a very long time. Worked in 16 different states. Seen a mountain lion scale the opposite side of a canyon in Utah, came across a black bear and two cubs in Wyoming, grizzlies and wolves in Alaska, gators across the southeast. All kinds of scary predators in tight quarters, scariest thing though was kind of square off with a cow moose and me and 3 other guys. They told us to hold our ground and yell and stuff in wilderness training but you tend to forget that stuff staring at a 1000 lb animal 20 yards from you. Mountain lion was something to see bouncing up the canyon face though, never forget it

Catch and release is always a good policy, sometimes them cougars can be a little dangerous!

Best ones I ever saw had the urge to get away quietly, secretly, those were good ones