I've had multiple generic or Bic brand disposable lighters go bad like that. The flint material appears to go to powder or just disappear. A couple were in survival kits, at least one was in a car glove compartment. My solution is to check them occasionally and have at least 2 independent fire-producing methods.

Steve
_________________________
"After I had solaced my mind with the comfortable part of my condition, I
began to look round me, to see what kind of place I was in, and what was
next to be done"