Looking at the general condition of that wheel cylinder, I'd suggest replacing it. The "missing link" there doesn't come out easily, especially on a properly-functioniong brake. I'll bet you're going to find a frozen-up piston in the wheel cylinder corresponding to the dropped link.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!