Americans, why you don't return my pen?

I had this pen which I bought at Ginza, Tokyo. My favorite pen and it'd been very good to me for several years. I decided to go school in Miami and in a class, a guy front of my seat, asked me if he can borrow a pen. I felt sorry for him not having a pen so I handed him my good pen, the best pen from Japan. But it turned out that it was the big mistake of all. As soon as the class ends the guy disappeared with my pen!

Dude, can you return my pen?

So I learned lesson not to hand in my best thing being nice and started to carry cheap Bic pens. I've handed pens to numerous people but I don't recall anyone returned my pen. It is almost like they don't need to return it... Is this why, in this country, they sell 30 pens in a bag? Why they don't return stuff they borrow... and when I ask to do so, "hey can I get my pen back?", what's up with that strange face?

It is a pen. I know. But that is not my point. The point is, you borrowed it so you return it with gratitude. Not stealing. Not giving dirty face.

And it would be nice to say 'Thank you' too, when you return it.