Oh no, did this happen to you? If so, I'm so sorry! (((HUGS)))
I've never been married or engaged, so it hasn't happened to me, but my stepmom's diamond came out while she was cleaning the oven and luckily she found it. If you have lost yours, just be calm, say a prayer, retrace your steps...you will find it.
I thought I lost my engagement ring once (was engaged to a different guy). I thought I lost it at work and I was going crazy. Come to find out it was at home.
This time around, I never take it off unless Im going to clean it and then I put it right back on.
If need be, check the vacuum bag. I'm sure it's there somewhere. You will find it. Give it a little time before going out and purchasing another unless of course you want a new one.