I'm pretty good at keeping pens. I used to lose lots of pens in school though, and I have friends who are very good at losing them, either forgetting them, dropping them, getting jacked for pens, etc... in result they have to borrow one.
Here's a solution that may prolong the loss of your pen.
"I recently discovered that four quarter-inch (1/4") neodymium disc magnets ("rare earth" magnets) will not only fit nicely inside the body of a Bic pen, but they are strong enough to hold both the pen and a shopping list to my refrigerator."LifeHacker found where to buy them here.
Now, when you lose your pen, you lose four neodymium magnets... plus your pen! That should be a little more reason to care not lose your pen.