Dereliction of Duty
Exactly.
He knew what he was doing and probably based it on the childish ‘it is easier to ask for forgiveness than permission’ premise.
He knew he would probably be replaced permanently so was trying to slip through without being discovered and some out with an ‘oh, btw, I had surgery three months ago’ confession.
What might have happened to a Sgt. for failing to call in sick, then remaining AWOL for a week?
Good to be/know the king.