Well I don't know anything about Fords, but I do know the clutch fork on my Chevy uses a retaining tab to clamp down on the throw out bearing. It is supposed to be there. One side of the retaining tab on the fork I removed from my truck was broken.
I did find this relevant Chevy place
to buy a replacement tab, but in the end I saw some small cracks on the fork and decided to replace the whole thing.
Which brings me to my next point, clutch forks are cheap. Buy a new one and be done with it. If it turns out the replacement does not have a retaining tab, then return it and keep using the old one.