This happened to me about 10 years ago, but it's a fun (to me) story I like to tell my junior staff to warn them about warm-and-fuzzy recruiters and headhunters.
I had just passed the licensing exam that would make me a Certified Engineering Geologist. My then-employer decided not to give me a raise, so I started looking around for something else. (In my industry, firms with multiple licensed staff prefer that the junior staff stay unlicensed to keep overhead down, which is bullshit, but whatever.)
I applied for a job as a Senior Project Geologist at a well-known geotechnical firm, but was never contacted. While I was applying for other opportunities, I reached out to an engineering staffing company to see if they could place me. The junior recruiter assigned to me, Dan [names changed to protect my horrible memory for names], found me an opportunity at — you guessed it — the same firm that I had previously applied to that never responded. Dan got me the interview, and I was hired immediately.
Dan's boss, Tania (senior recruiter) called to personally congratulate me for getting the job. I had never spoken to her before and she had no hand in placing me, so it was weird that she was being so aggressively friendly. Then she asked me if I knew anyone else who was looking for a similar position, since they were working with multiple firms who were desperate for qualified geologists. (To this day, the same staffing company calls/emails me regularly to see if I have pals who need a job.)
The position at the new firm wasn't a good fit, so about 5 months after had I started, I put in my notice. A few days later, I get a heated phone call from Tania, yelling at me on the phone that I was VERY UNPROFESSIONAL TO QUIT LIKE THAT and HOW DARE I PUT THE STAFFING COMPANY IN SUCH A POSITION and THEY WILL NEVER WORK WITH ME AGAIN. (They still call me, BTW.)
Turns out: the staffing company had to pay back their commission (roughly $60k) to the firm where they'd placed me. Since I never signed any contract with my employer (or the staffing agency, for that matter), I had no obligation to stick it out.
(As an aside, when I was onboarding at the firm, I told the HR guy that he could have hired me without paying the commission if he had responded to my initial application. I'd never seen anyone's eyebrows raise so high. Oops.)
I did, however, take exception to being yelled at on the phone by some random recruiter who did nothing to place me (Dan was the MVP), so I composed an email about the incident and sent it to her corporate office. A couple of weeks later, Dan emails to tell me that Tania was fired over the incident and that he had moved on to another staffing company.
And also, that he would love to place me again.