So I opened a portal to the Outer Lands and explored the entire dimension, however, the tablet was missing. I found the room where the tablet should be, but it is missing. The gate is still shut so even if this is someone elses portal somehow, they never used it.
I have never got this far into Thaumcraft, But I shall tag @Moderator and see if they know anything about it.
Itemclears sometimes cause this(from what i hear), they need an exception for runed tablets specifically
Was the boss still there? If not I assume a other player got it I also can't test if it is possible to remove the tablet with a item clear as you removed the pedestal where the item is normally on I think.
Boss doesn't spawn until you open the door. No one was there before since it created new terrain when I first made the portal. I removed the pedestal since there was nothing there.