I have. Pretty scar and very dramatic. A friend saw one come through the wash by her house. Big wall of water, lots of noise, boulders, etc. Not a cloud in the sky.
I've been going to the desert for many decades...There are flash flood washes everywhere below high ground...If one is stupid enough to go into a wash before or during heavy rains...??? lol....
Those that know, or have a brain, know it can happen miles away up in the mountains...Water goes down hill...No surprise..
My point is, most flash floods occur where no one is most of the time...Those dumb enough to be in OR live in low ground flash flood areas.....Well...what can ya say? They're going to get wet...