The Jacobson-Lockhart backstory is in Lockhart's character profile, which makes it hard to find. I'm going to copy it to here:
QUOTE
The Lockhart-Jacobson Backstory
Jacobson, working as a Healer on St. Mungo’s closed ward, tries an experimental unapproved cure on Lockhart. Lockhart appears restored to his original mental capacities – remembering everything – for a couple of weeks, but then lapses back into to a more befuddled state, having decided that being a bit of a half-brain he will be better able to exact his revenge.
Jacobson, although he is mystified by the relapse, decides that Lockhart is well enough to leave St. Mungo’s. Jacobson’s wife, Alison Wiles, has just taken a job as the astronomy teacher at Hogwarts, and through her he discovers that there’s an opening for a charms teacher that the headmistress is having difficulty filling it. He suggest to Lockhart that he apply.
McGonagall is in dire straits for a Charms teacher. Although she has reservations about his abilities, she also feels guilty about what happened to him during his previous tenure at Hogwarts. She gives him the job.
Jacobson becomes worried that Lockhart might either spill the beans about his illegal cure or might have a more serious relapse. Wiles assures him that she will keep an eye on Lockhart, but Jacobson continues to worry. He decides to quit his job and move to Hogwarts with his wife. Wiles argues that it will seem very suspicious for a high-profile healer to just up and quit his job. Knowing that the current Transfiguration teacher has been thinking about a sabbatical, she convinces him/her to take it this year. When McGonagall starts looking for a replacement, Wiles suggests her husband, and the deal is sealed.
Lockhart, of course, is only pretending to be muddled. In reality, he's using it as a cover to plot his return to fame...
He has at least one puffskein around him all the time, usually provided to him by Wiles & Jacobson (for their soothing nature, as part of his cure and recovery) and by Luna, who just thinks he loves them.
It that illegal cure that Jacobson is presenting to the council. Of course, he's not mentioning that he's already tried it on somone. Does that make sense?