If you used your EAD for a short period of time, the USCIS might not care about that and then, they approved your H-1B transfer. In my point of view, you just keep going and continue to work with H-1B status because it is difficult to explain this to USCIS clearly. Also, it is not your fault. I do not think they will pay attention to this in details when they process your I-485 application.