While anything is possible and there are many unprofessional therapists out there, technically this shouldn't happen with a decent therapist. First of all, that person's therapy is confidential, so even if they talk and the therapist realizez it was you, your therapist cannot bring it up. On the other hand, a therapist needs to be able to contain conflicts like this. It's not even as if you were related to this person, it's a one time thing. There isn't even a conflict of interests, though I understand how this may feel uncomfortable. I highly doubt that your therapist will terminate your therapy just because you got into a disagreement with some other client.