Could My Doctor Have Inadvertently Nicked a Blood Vessel?

Whenever a face/neck lift is performed, small blood vessels are cut as the incisions are made through the skin and as the skin flaps are raised.  It is normal to cauterize these vessels to stop them from bleeding.  Normally, this should not cause a burn on the skin, unless the bleeding was possibly coming from the skin side of the flap.  I would discuss your issue with your surgeon, as he would know exactly what was done during your particular procedure.    

     Thermal discharge from electrocautery used to stop bleeding can cause burns from beneath the skin that may be seen on the skin's surface.Kenneth Hughes, MDLos Angeles, CA

All I can do is speculate what may have happened. I would recommend that you ask your facial plastic surgeon why you have the skin changes that you discovered. As part of facelift surgery, one routinely encounters blood vessels that need to be sealed with electrocautery. For this process to take 1 hour is rather unusual.