Lost/stolen promise ring

So I need advice. A few weeks ago my boyfriend of 2 years gave me a promise ring. I have been wanting one for so long and one night, it happened!!

My grandparents are highly religious and they are trusting and worried about what I’m doing since I’m 19. When they found out I had the ring they lost it. They consistently questioned me about if I had plans to elope and if I was wanting to get married. I told them the truth though. Which is no, I have no plans of getting married anytime soon. I’m too young and I want to live alone before I share my life forever with someone else. Plus, what’s the rush? They wanted to make sure he was aware of this and I told them yes (the truth). Well yesterday, I was going to wash some dishes. I put my ring on the window sill like my grandmother does when she’s washing dishes. So after I finished, I made myself a cup of coffee and left for work. Without my ring. When I get home I eat my dinner, go upstairs, shower and go to bed cause it was a long day. I wake up this morning and well, the ring wasn’t there. After discussing it with my brothers, they said my grandmother made a comment about the ring last night and then took off upstairs. Lots of things just disappear in my house. But I think it’s kind of strange a comment was made and now it’s gone. These are big accusations for me to be making and I just don’t know how to approach the situation. My grandmother can get very hostile. But the ring was expensive and it was his moms. I am so mortified and depressed. Any advice? Am I in the wrong to think this way?

*UPDATE*

She says that she doesn’t have it and has no clue what happened to it. We got into a big argument though and it’s resulted in both of us being in a bad mood. My grandparents don’t want us to be together. They don’t want us to last. It’s not like we were planning to get married at a certain time or anything but we do want to eventually get married. When the time is right. They think I need to date other people before I just settled down and chose to spend my life with someone. I just don’t understand why. He’s a wonderful man. He’s so good to me. He surprises me at work, he tells me he loves me and I’m beautiful every single day, he opens doors for me and respects me. He treats me like a queen. I just don’t understand why they feel like I should go whore around before I finally find what I already have. Any advice on how to handle this? They are extremely controlling and honestly, not very understanding when it comes to relationships with me.