Mine just randomly stuck once too. It freed itself, sort of... I had been poking fun at a friend because his Audi 90's trunk release wouldn't work, and the key wouldn't open the trunk either. So I said, "Hey, you know what? Look at this!" and I tossed my keys into the trunk (because the car was unlocked), shut the trunk and proceeded to pull on the trunk release handle... to no effect.

I never figured out why it stuck right then, I ended up pulling the back seat off so I could get my keys. I did remove the spring on the handle (since it was ineffective anyway) and I've never had an issue since...
My car is more humble than I am.