I have played through a couple times and beaten it on legendary but now they are all gone any suggestions? to get them back?
other than play through again
Unfortunately running through the campaign again is the only way to “fix” it. It’s happened to me a few times. Just run it on easy and it’ll all be unlocked for you again.
Go through on normal and get your commendations up. 
(I don’t know if you have them done or not, but the campaign in fun anyway) Also, I’m not trying to be offensive, I just like the campaign.
Play through it.
Oh… you said besides that.
Okay, what you need is a half cup of sugar, and a full cup of water…