Something similar has happened to me on my Prius bluetooth connection once. I have a LG VX-8100 Verizon phone, and the car thought that bluetooth was still connected (after disconnecting the call), but the radio had started playing. I had to turn the car off to fix it...
Since it didn't happen again, and I have never been able to duplicate it, I wrote it off as the bluetooth gods messing with me...+G