Yesterday I had an interesting experience, tooling down the highway at about 3000RPM when I decided to punch the kick-down button (under the gas pedal) to pass. The transmission did indeed gear down like it's supposed to, but then I looked down and the RPM's were at 5000 and climbing! I immediately moved to right lane and let off the gas to pull over, but had to keep going for a bit before finding a suitable spot.
I was able to slow down, and still could feel the gas pedal accelerate the car while I was doing so. As this was happening, I was still in gear (D), I then noticed that pressing the gas had no effect on the transmission, as if it was sitting in P at idle, just revving with no actual power getting to the driveshaft. All pushing on the pedal did was blip the tach reading. Ohmygod, I thought, I've blown the tranny!
At that point I slowed enough to stop by the roadside, which I did, putting it in P and leaving the engine idling while I struggled to disconnect the kickdown switch, which was stuck, as I suspected.
End of story, it went right back into D and accelerated, shifted up/down like nothing had happened. I'll replace that damn switch soon.
My question: Is there some sort of fail-safe mechanism in the transmission that disengages the drive gears when the unit is over-revved in a lower gear than high? I'm wondering why the transmission 'cut-out' just before I actually coasted to a top, still in D.

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1986 560SL
2002 Toyota Camry
1993 Lexus