I have been reading Reynolds's space opera Redemption Ark. In it, the villain Skade attempts to have her ship make a "state 4" jump, meaning jump to a faster-than-light speed. At the heart of the jump is a machinery that creates and contains a state 4 quantum vacuum. A state 4 vacuum is exceedingly difficult to contain, and things go awry. The machinist operating the machinery claims she cannot find a co-worker. He was here a minute ago, she claims. But his name doesn't appear on the crew list. Skade gets curious and runs a research on him. He turns out someone with the exact set of qualifications that would have had Skade recruit him to operate the quantum-state machinery on her ship, had he not perished in an accident some years ago. The plot's implication is that a quantum instability resulted in a timeline jump, changing history to an extent. I remember reading this exact same scene in another book. A complex machinery "disappears" an operator. In the newly-created history, he had not been there working at all. No one can remember him except one co-worker. The story offers an explanation how the lone co-worker happens to remember, but everyone else has forgotten him. It was probably by another author, but I cannot exclude Reynolds entirely. Possibly it was a short story. I cannot remember which book and it's driving me crazy. It's a long shot but I decided to post it if perchance someone might remember and be kind enough to respond.