Console players who have Diablo 3: Ultimate Evil Edition had issues with losing Legendary Gems after a hotfix. Blizzard is now fixing the issue by issuing replacement gems.
The hotfix was intended to lower the cost of regular gems in the first place. In particular, this fix was meant for regular gems used to enchant a ring or an amulet. This change will instead be sent out in the next major patch.
If you were affected by losing Legendary Gems, you can check your in-game mail, which will have the replacement gems. These replacement gems are ranked higher than the gems you lost.
Before you open that mail, however, make sure you have enough space in your hero’s inventory first. PlayStation 4 mails will have your username in the sender field, but Xbox One mails will have no name on the mail, and a blank sender field. Of course, you also need to be logged onto your SEN or XBL account.