Read your story and have you ever tried to get in touch with Blancpain? Maybe they are able to help you on this. Should not be a too big issue, IF only the screw needs to be added. Nevertheless, do not forget, once the case is opened, the case back gasket should be exchanged, too, just to make sure
Dear Alan, There might be a chance that one company can help you. What you need is to send the dial with the pic of the original state (you have the pic from the watch in Omega Museum) to them and until now I only had positive surprises. In view of quality and price. Firma Richard Bethge GmbH Karlst