[Earendilyon]

Originally Posted by AragornII

This sounds like the dwarves had access to Thorin's tomb, if they could tell that Orcrist was glowing.

From you own quote from The Hobbit:

Upon his tomb, the Elvenking then laid Orcrist, the elvish sword that had been taken from Thorin in captivity.

So, the sword lay upon Thorin's tomb, not in it.