I have many clients who ask me during our initial consultation about either the engagement ring or the wedding band or both. Sometimes the ring in question is a family heirloom, sometimes it is an expensive piece of jewelry and one time it was a piece of art actually made by one spouse-to-be for the other.
Whatever the source of the request, unless there is specific evidence to support the claim that the gift was conditional, like a written pre-nuptial agreement, the answer is the same: no you can’t get the ring back.
In more than three decades of handling divorce cases in Missouri, I have yet to see a pre-nup that addressed the return of an engagement ring or a wedding band. I would guess that such a request would be cause for calling off the wedding.
Oh, and if the wedding is called off, the bride-that-was-not-to-be gets to keep the engagement ring.