Question: Can any thread have a thumbnail?

I made a thread recently, and when I made it, it asked me if I wanted to add a thumbnail. I was worried whether I might have done it wrong, so after I posted the thread, I made sure to take note that I did indeed add a thumbnail.

When I came back to the thread a few days later, I noticed that the thumbnail was gone. I'm wondering whether it was removed, or whether I really was just not paying attention as much as I thought I was.

to more directly answer your question - yes

no one edited the thread to remove the thumbnail though so it was probably you :P