2005 GMC Sierra driver side heated seat

I have an 2005 GMC serria pickup, I had the driverside mirror (remote, heated and blinker) replaced at the dealer and after that the heated seat on the drivers side now does not work. The light on the switch will not go on.I thought that maybe the serviceman forgot to hook up the wire, but the dealer said that there is power to the switch and out of the switch. The heated seats worked ok the day before I took it in for the mirror replacement.. Any suggestions as to what is wrong??? The passenger side heated seat does work...