couldn't see the ring of my band during an EGD?

I had an EGD and a colonoscopy yesterday for another issue I don't need to go into here, but the doctor said I should have a UGI series and follow up with my band surgeon because he "didn't see the ring" of my band and he thinks it may have slipped (they actually used the words "slid down" so I'm assuming we're talking slip here). 

Should the ring be detectable from the inside during the endoscopy process?

Thanks,
Jan