A childhood belief about sucking my thumb

I was a well-known thumbsucker during my childhood. I tried to hide it as much as I could, but occassionally, I'd get caught. An uncle of mine once told me that when you suck your thumb, it shrinks and will eventually fall off. The uncle would reference my now-deceased grandfather, who only had half of his right index finger. I was told "that's how Grandpa lost his finger... he was sucking it too much." I was terrified, but couldn't stop my habit. Instead, I'd try "spreading out" my sucking, trying to not resort to my thumbs all the time, but to try my index, middle, ring and pinkie fingers as well (didn't work). Although I obviously didn't think about this threat daily after a certain point, I remember coming to the realization in high school that something I had always believed... that sucking your thumb will make it fall off... couldn't possibly be true. I asked my father and sure enough, Gramp lost his finger in a work accident while he was a ship builder in the 40's!