As stated, redeemed 80 Defiant Engrams & about 90 Wish engrams in one go, didn't think the mailbox would eat them, but the mailbox absolute ate them. Anything that went to the mailbox is not there. I've tried relogging, I've tried giving it a couple of days, nothing. I know it's all gone because I had about 15 Upgrade Modules that have been slowly stacking up for about a week at that point, and those are gone too. I'm going to assume this is just one of those 'too bad' situations with no fix, but it's kinda lame that this is possible.