It happens all the time. I've been in a similar situation. Denied a promo because of anonymous feedback from someone who said I had "communication issues". Probably not sexual in that situation as I never hit on anyone at work or had any desire to, more likely I asked them to (re)do their work and they took it personally given the context at the time. Nobody would tell me what I'd said, or to who, or what I should do with such feedback.
My actual communication skills were not the issue, mind. The company frequently asked me to write and give presentations, either in public conferences or to the rest of the firm.
Anonymous accusations that sink careers are a plague of the modern workplace and are entirely due to a culture of "always believe the victim".
