[dutch husky]

I'm guessing either you slightly let go of the button (I've had that happen before, where I was holding it but moved my finger and it "let go" even though I didn't feel the button un-click), or you went over a bump.

I too have had this happen, if my fingers relax and let the paddle out ever so slightly, even though its not enough for the physical "un-click" to occur, it does seem to be enough to disengage the electronic switch in the paddle.

Driving over bumps also can make the car feel like it momentarily surges forward. I've experienced this in other cars besides the Volt, as well, with their ABS systems. But it feels slightly more pronounced with the Volt's regen.