All shirts have been paid for in full up front so IF the shop hasn't paid the supplier yet as a business owner myself i would be asking for a discount per shirt due to the huge balls up and then pass that on to the fan with a part refund, again that's IF it's the suppliers fault.
If it's the shops fault for poor communication to the supplier then the shop should be offering every single person who has purchased a shirt some sort of good will gesture, what i don't know, maybe a basic devils t-shirt that fans could use to get signed when they have the team signing night.