You've eaten there before, you'll eat there again, and you're having dinner there, so yes....you can calm down. Who needs to eat in some stinky enchanted ballroom twice in one trip?
Hope that helped. Now, as to your original post, they lost mine too last month, and I didn't find out until I went to check in and I. WAS. P-O'd!!! It wasn't the CMs fault, and I know that, but I also know I did it all correctly, down to screenshotting the confirmation. They couldn't find it anywhere, and I refused to move. I was really trying to stay calm at check in because I knew it wasn't their fault, but we had had such a horrific short trip with MagicBands and were hours away from Magical Express, so I was at the height of my emotion.
It was not fun. I was really upset about it because I had spent the whole weekend dealing with MagicBand issues and My Disney Experience problems (including lost FP), and I think someone inadvertently just wiped our entire profile, including the BOG lunch passes, so it was the final straw.
Luckily, they could clearly sense my reaction, and they took my mom and I in despite not being able to find the reservation. I wouldn't wish the stress on anyone...so, for you, I would just savor the flavor of your dinner - ENJOY!