This happened to me when it was time to move on from my first real job. A recruiter, who I spoke to briefly and had no interest in moving forward with, contacted my current manager and said he'd help fill my role after I left. My manager had no idea I was looking to leave at that point. After confirming with me that I was indeed planning to leave, the manager wished me well, then ensured neither the recruiter nor their company would ever work with one of the largest engineering companies in Europe. That felt righteous and worked out for the best, but could really have left me in the lurch.