This must be very common. It happened to me in Long Beach, California, in 1999. A ground handler asked me if he could use the GPU attached to my Learjet 35 to start another aircraft. As I was not departing for another two hours, it was fine by me.
He jumped on the tractor and drove away, without disconnecting first.
It cost their insurance carrier about $30,000 U.S., because they had to provide me with another Lear 35 while the damage was being repaired.
And Hi-Vis vests did not help at all!! Sorry, I could not help myself there.