Lost necklace fiancé gave to me

My fiancé gifted me a really expensive David Yurman necklace and I lost it. I typically wear it 24/7 except to shower. I noticed after my shower it was gone. I had on a bracelet I also take off to shower.

He’s really busy and stressed out with a work project so after searching for 30 minutes and checking my person to ensure it wasn’t on me,

I went for a walk.

Idk what to do. It has to be somewhere in our apartment but I don’t know where. I got back and immediately checked the couch cushions and I could tell I was bothering him and they were not there so I stopped looking.

I know he’ll think I lost it on my walk and that I shouldn’t have gone. I’m devastated it’s missing and don’t know how to tell him.