Missing suit - advice appreciated

Hi everyone,
Wedding is 4 weeks today and I'm really at a loss! After a disastrous dress fitting this week, where my bridal shop has taken my dress in way too much, my partner has revealed to me that the popular hight street chain he has got his suits from has lost 1!
I really don't want to burn my bridges with the store yet. Basically, does anyone have any suggestions on what I should do to resolve this? The suit in question is for a person who lives 2 hours away. They first came up to be told a suit would need to be specially ordered for next time. Visit 2 - whoops! The store forgot to order it! Visit 3- Hooray a suit! But far to big so sent off for significant tailoring. Today my fiance goes to pick up all the suits and guess which one is lost?! What is the calm, rational way to approach this? 4 weeks is too late to start again and groom had to have a bespoke size made which cost a small fortune. My heart wants to go storming in and demand a full cancellation and refund, but my head says we really need this shop to pull up its pants and get this sorted. Whatever way, our groomsman is going to have to travel up again which is costing him! Should I contact head office? Should I threaten bad reviews? Do I give them yet another chance even though I have lost complete faith in them?