Why "LOL"? It's true.

Of course, if they'd ever had a similar painful experience (heavy weight dropped on flesh and bone), and you had no obvious reason for making up the whole thing, their most rational opinion would be that your pain was a fact - until the Styrofoam evidence surfaced.

At that point, they'd wonder what you were after.

Amputees frequently report itching or other "feeling" "in" the amputated limb.

The experience of the feeling appears to be a fact (according to   medical opinion). But if the amputee insisted, on the basis of his presumably factual but subjective feeling, that the limb must still be there, that opinion would be not only false but crazy.

And, of course, just because the feeling (called "phantom limb syndrome") is a widely accepted fact, that particular individual could be lying about experiencing it personally.

Short of a brain scan, what way would there be to tell?