This forum has had dozens of threads on this subject.
Whenever an Elder Rift has crests added to it by a player, and that player doesn’t complete the Elder Rift (e.g. sometimes the zone-in teleport fails / takes them to Wortham, or they crash, to they elect to leave), the crests will always be sent back to them via the in-game email. This returns process is not instant. It can take some time. But the crests are always sent back to the player.