My raid team has experienced this twice where the Swordbearer will drop the relic sword, one of us picks it up only to have nothing happen and the sword disappears. Wouldn't be too big of a deal except now you have two Gatekeepers with full health waiting on the other end that need to be killed with the next sword drop.
Video: http://youtu.be/S-sw1b710mM
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You don't even need to kill the gatekeepers lol