Regarding the myth of the godly essence/artifact, no mention of it ever says where it fell or even if it fell to Toril. Some speculate that perhaps the essence is the moon it's self or the tears that follow behind it, others mention the morning star as being the pice; still, others say that it ended up in, or becoming the Positive Plane or being lost somewhere in the astral plane.
Just as you are about to give up on the search you do read one very small snippet that, of all things, Gnomes believe that a shard of some god lies deep in the center of the world and is a gem of the purest and most beautiful makeup to behold.
There is not much written on the death and destruction of celestial beings in this library.