I guess I'll worry about it when and if it happens to me. But no, it's certainly not something I think about on a day to day basis, just as I also don't worry that someone might steal my car in the middle of the night and commit a crime with it -- another scenario in which, yes, you may also be arrested or at the very least questioned.
I'm inclined to believe that such arrests are quite rare, but that's just speculation, and I'm open to evidence to the contrary.
If I find myself in possession of a cocaine brick that I did not ask for, I will indeed worry. The point that the article made (as a tangent, admittedly) in regards to cocaine possession is that, should that situation arise, I can't take my cocaine to the police without risking arrest myself, and that's absurd.
This is supposed to be reassuring?