When I was very little, I used to steal my mother's couch pillows and spit on them. I would then lay my cheek in the spittle and suck my thumb. I can sort of remember why I did it too. I remember that it would make the pillow cold. I still like a cold pillow under my head although I don't hock up loogies much anymore. My mother said I ruined lots of couch pillows until finally I started using one that had a removable (and therefore washable) cover. 
He has a terrifically original name of Goldie (short for Gold Pillow) and I have him still. He is flat and his fabric is weak. I can't lay on him anymore for fear of tearing him more than he is already torn, but he is still my lovey. My sister tried to repair him for me once but he's just that old, he tore again almost immediately (she said, "You weren't supposed to LAY on him anymore stupid!").
Out of four children, two of them sucked their thumbs and both of those two children had loveys of their own. Ty carried around a ratty old crib comforter imprinted with dinosaurs. He used to stick the corner of the blanket in his ear, in the corner of his eye, up his nose and in between his toes to make it smelly. It was almost like a ritual; I would wash the blanket and he would immediately try to make it dirty and smelly again. After a while not just any corner of the blanket would do. He had a specific corner he particularly liked. His blanket's name was Cornie. He stopped sucking his thumb long before he outgrew using Cornie and it was a sad day for me when he decided he was too big to sleep with his baby blanket anymore.
E had a much odder "lovey". She used her belly button. I know, I know, that's weird but it's true. She used to stick her finger in her button and pop her thumb in her mouth. She had a very funny Pavlovian response - If I stuck my finger in her belly button she would still pop her thumb in her mouth. I wonder even now if I touched her belly button if she'd start sucking her thumb but it hasn't been that long since she broke the habit and I don't want to tempt fate by trying it out.I can usually tell when someone was a thumb sucker. Most of us have a very slight speech impediment, so slight that I think most people don't notice it. We thumb suckers tend to have a slight "th" sound to our "s." I was lucky that my mother has her masters in speech pathology so when I'm not being lazy I have very clear diction but both my thumbsuckers have that slight "th" sound. We were watching MindFreak on tv last night and I suspect Criss Angel was a thumbsucker. Next time you're talking to someone, listen for it. Maybe you'll be able to tell if they were a thumbsucker or not.
I suspect my sister could tell you whether someone has had braces on their teeth for the same reason.
