RhoGam and passive antibodies

R • Due 9/7 with my first little one. 💜💜
I am Rh negative, and just tested positive for antibodies 15 weeks after I got RhoGam with my miscarriage/D&C last October. Going to call my doc, but has anyone had experience with this? Is it possible that the antibodies are from RhoGam and I am not actually sensitized? How long can the passive antibodies from RhoGam remain in your system?
I know that only my doctor can answer what is specifically going on with me and my blood. I'm curious as to what other women who have been in a similar situation have experienced.