Missing pens

It's a fact that my father-in-law is not buying those expensive ballpoint pens anymore. Everytime IBS#2 comes over with her two bratty kids, those pens are sure to go missing. And he will rant in the middle of the night cos he cant find them anywhere. I think you can understand his angst. He keeps themhigh up on the cabinet and yet, they still go missing. He cant understand as to why they know where he puts them. He says it's discount pens this time. Gonna buy them by the cartons this time, lol.