Disclaimer: This is not my original idea. I'm just passing it on.
Step 1: Materials
Something liquid that hardens into something solid.
Step 2: Mix Up the Liquid That Becomes Solid
Pour some in a paper cup.
Stick the pen in it cap side down.
Wait for the Liquid-Solid Transition Event.
Peel off the paper cup.
Step 3: Oh, I'm Sorry, Is This Your Pen?
else they will dry out.
They don't like that.
And your pen is now less likely to end up in someone's pocket by accident.
Not impossible, just less likely.