It's common. The glue gets weak after a while. The trick is to be sure to put it back in the same place. Get the kit for this- trust me.
You have to first remove all the old glue, then use the glass etching solution, then the proper glue. Or it will fall off while you are driving and scare the you-know-what out of you.
Trust me, I know. My soda straw went right up my nose and I bled all over my hamburger and fries.
Funny to think about now, but wasn't back then.