Doctors grrrrr help!!! Polyp

So today I went for a hystocopy for a polyp removed that had showed up on a ultra sound and there was nothing there !!!!! Does anybody know what it could of been ? I didn't ask the Surgen at the time just wanted to go home. We have been ttc for 8 months now and have really painful heavy period exept my last one and he just said oh well it should be ok then afterwards ! Help ! Thankyou