How soon after you did the tune did that happen? I'm just guessing here but it sounds like the computer just had a little hiccup. Sometimes when sensative electronics like the computer gets too hot, it with malfunction. So if you did a 93 octane tune and you still had 87 octane in the system then maybe the engine was running a little warm?
I have a similar issue on my 90 ramcharger where sometimes it will get stuck in overdrive off even if I didn't turn it off and the only thing I can do to correct it is to turn off the engine and turn it back on again. I don't even have to turn off the ingintion so, idk maybe our issues are related.