This is the 2nd time this has happened & im pretty sure it ONLY happens with time capsule unattuned gear. I mailed the complete set of enhanced dark raven gear to an alt, i had 4 days left to get it b4 it's supposed to return to the mailer (my main). I had real life things goin on & couldnt playduring that time but it never came back to him & is just gone. It hasnt returned on any of my character's mail. This happened about 2 years ago with another set of gear (cant remember the name) from time capsules and i thought it was just a 1 time bug but now im convinced it happenes with all the time capsule gear. Too much coincidence. Its the only thing that doesnt return. Base items, collections, in game gear drops, etc ALL come back, time capsule gear does not.
And this is why you should transfer gear using your SHARED BANK, rather than by Email. The rarer the gear is, the more important it becomes to use the Bank, not Email. The in-game Email system has always had issues.