what he does in his own time is his business, but if it affects your work it is yours, I would lay down the line, and say to him if hes crosses it he will be unemployed, simples 
he lost a pole the other day, told him from now on anything he loses he pays out the wages ,he knows im on to him
He might have used it as a roach for a joint.
He could have fixed one end to the water tank, used the pole to draw smoke through and the water tank as a giant bubbly pipe. It's all the employers fault anyway. Fancy letting a young lad near resin and not explaining what it's for.