iPhone 3GS won't turn on

I plugged my iPhone into the cigar lighter of my car using the Griffin PowerJolt (for the first time). After about 30 mins the phone turned off and I can't turn it out again. I tried plugging it into the power adaptor for a while and then tried turning it on. I tried resetting it (by pressing the home button and sleep/wake button) while it was plugged in. I tried connecting it to my Mac to see if it appears in iTunes. I tried putting into recovery mode by connecting usb cable to iPhone (while the other end was plugged into MC) while pressing the home button. Nothing seems to work.

This appears to be an ex-iPhone. Any ideas?

Thanks