"I Think That I Am Damaged, Damaged, Damaged. So How You Gonna Fix It, Fix It, Fix It?"

A few weeks ago, Quincy's thumb got stuck in a bent position. (see photo below) She was hysterical. Screaming. Freaking out. We thought it was broken at first, but there was no swelling, and it happened when she was just playing with her dolls. But she was crying and screaming like it hurt. I grabbed her hand to take a closer look, and her thumb "popped" back into place.
Crying stopped immediately. "You fix-it my thumb? Oh thanks, Mom!" and off she ran, happy as can be.

This happened a few more times over the course of a few weeks, and now the frequency is increasing. From once a week, to once every few days to every day, and now 4 times TODAY. She no longer screams and cries, but it still freaks her out a little.

She'll run up to me, show me her bent thumb and say, "fix my thumb, Mom! It's not working!" I'll pop it back (yes, it takes a small amount of pressure/force...but it does go back) and off she runs.
What is wrong with my kid's thumb? This is the thumb she sucks when she sleeps...could that be related to the problem? Has something similar ever happened to you?