Interesting read. I've locked up the rear before, but the bike didn't fishtail like yours. Had it, I would've gone down because I was going about 60. The other fun experience I had with the rear coming out from under me was while going DOWN a mountain road into a sharp hairpin. I thought I was downshifting to 2nd gear, and so didn't blip the throttle much to match revs, while I was actually shifting into 1st. Well, of course, as I released the clutch the engine screamed about 2k rpms more than I was expecting and the rear started to go out. That was wicked fun though
I held it out there until about midway through the turn and I was only going about 20mph, so it wasn't like I had to change my pants afterwards.
But kudos to you for not crashing and holding it together.