for once, i can see a use for j.b. weld here.
I would j.b. weld the pin in place to keep it from falling out.
since there really isn't a load on it, j.b. weld will hold it in the hole fine, and keep it from falling out.
Some pop rivits are made of aluminum tho, not sure how long it will last. (if you have an aluminum one that is)
if you do j.b. weld it in the hole, make sure to clean the hole and the pin VERY good, or the j.b. weld won't stick.
I would reccomend j.b. welding it in the hole just to keep it from falling out later on.