Engagement Ring w/ Moissanite stone

One of the stones in the 2nd band is missing, we had bought it with the 2 bands(not considered a wedding set) and it has I think a 1carat moissanite stone. It’s either half or 1, I don’t remember too much. I’m asking $500 or just best offer. It’s also either a size 8.5 or a size 9