This isn't the first time I've heard of such a thing. From
When the Air Hits Your Brain: Tales from Neurosurgery by Frank Vertosick Jr:
> “He’s a big fan of yours, too, pal, ever since the bone flap thing.” The bone flap incident had occurred early in Gary’s chief year. Fred and Gary were performing a cranial operation to remove a benign brain tumor. Fred had performed the entire operation himself—a grave insult to a chief resident, known as “stealing the case.” After Fred left the OR, further irritating the chief by dumping upon him the tedium of closing the wound, an angry Gary had engraved the phrase “Fred sucks” with the electrocautery knife on the inside of the bone flap, the plate of skull bone that is temporarily sawed away to gain access to the brain. He had then wired the flap back into place, thinking that the inside of the patient’s skull would never again see the light of day. Unfortunately, the bone flap developed a staph infection and had to be removed a week later. Once contaminated with bacteria, the free piece of skull must be removed to cure the infection. The soft spot is filled in with plastic several months later. Gary coerced me into assisting Fred with the surgical removal of the infected flap. I’ll never forget the almost unintelligible stream of invectives that spewed forth when Fred saw Gary’s skull graffitti. Fred was too embarrassed to send the discarded flap to the pathology department as it was, and we spent an hour drilling the message off the bone before allowing it to leave the OR.
Considering the type of personality that surgery attracts, I see why this happens. That said, I don't think this is a common occurrence. (And it should go without saying, but such actions are unethical, unprofessional, and worthy of criminal charges.)