Alecadi, you ordered by credit card?
OK, Send an email and a letter (with proof of delivery or other service) cancelling the order. If it does magically shoip, refuse the parcel.
Call your credit card company and find out their proceudre fro a charge-back, they all have them. You ordered goods by rush delivery, nothing has shipped. You've tried to contact the merchant and no one responds to multiple contact means.
The credit card company will reverse the charge. Now you can order keys from someone who has them in stock and knows how to ship them. And at this point, you might just use Priority Mail. It isn't guaranteed second day, but it is a whole lot cheaper for "usually 2-3 days" service
Meanwhile...I think a number of members have remarked that just about anything will fit in the Yanmar keyway. Check any keys or shims you have, they'll probably work.