I once got a tampon stuck (forgot it was in and had sex, so the string ended up in there). I could feel it, but couldn't get a grip on it from the angle from which one is forced to retrieve such things. I had to get my husband to get it for me. I was totally embarrassed, but I kept imagining myself in the ER, and that would be far worse.

Can you get your partner to help you? I'm assuming you have one, or you wouldn't have had the diaphragm in in the first place.