Michelle, you have three options here:
you can look at another stone in stock for your setting
you can ask David to find another stone similar to the one you were first looking at (not always possible to replicate exactly what you were looking at, but he has access to some of the finest cutters in the business, so there's a good chance you'll be able to work with David to find a suitable stone)
You can wait and see what you think of the custom setting being made for the stone you first considered. It might leave you cold, but then again it might, just might, knock your socks off!
You never can tell. Sometimes a stone I had in mind for one thing is set in something completely different, and I suddenly realise that David is a genius and it was meant to be.
Whatever happens, we can work with you to get something that's just exactly right, if you'd like us to.