This made me chuckle.One day I unplugged his keyboard just to see if he’d notice.
He went for over a week without logging into his PC and realising.
I did something similar to a technician some years ago who had, up until I arrived been left to go feral in the lab at the bottom of the plant.
He was producing suites of results which looked very similar, so one evening after he had left I took the batteries out the penetrometer needle and the fuse out the plug from the roto-evaporator kit. Without these it is impossible to recover and test any binder.
I said nothing for a week, and as I was generally spread about the whole of the SE England I never saw him until he then produced a weeks worth of results. I produced the battery and fuse, he spluttered and muttered, we came to an agreement about productivity and toeing the line and it ended amicably (after a fuckton of supervised re-tests).
In the end he smartened up and became a good tech.