In the quest Saving Last Refuge, you fight the Idol of Loathing. After killing it, a time rift to the ancient era opens. I activated the time rift, travelled there, and then went immediately back through the time rift again. Now the time rift is missing from the area the Idol of Loathing was in and, I could not progress.
Workaround: Portal out and to the area again → Idol of Loathing respawns, kill it, time rift opens again.
Player log:
Player.log (325.5 KB)
(I made the bug report minutes after it happened.)