Wow. Funny the same thing happened to me for the first time today. Backed out and it just kept going. I put it in drive and then hit the button to turn off the sensors and it went on for a few seconds then finally turned off. Very odd.
2012 Crystal Red Volt, All options except Navi.
VIN#C-3498 Born 09/11= RIP 11/28/11 with 1600 miles.
2012 Blue Topaz Volt/ Loaded with every option adopted 1/12/12 with 9 miles
VIN#C-7622 "AC2DC" EV Personal best= 58.1
Current lifetime MPG=103
2012 Toyota Prius Plug-In
Adopted 11/5/12 with 3 miles
"American by birth, Teamster by the grace of God"