Found quest items while mapping

I entered the Sealed Vault using a waystone along with some kind of
Idol. While exploring, I came across two Small Soul Cores.
I believe these are usually quest items during the leveling process.
But I’m not sure if that’s the case here or if they’re supposed to
drop in this map.

After finishing the map, I couldn’t find any use for them, so I
teleported out. When I checked my inventory, the cores had
disappeared.
I went back into the map and saw them on the ground again, and I was
able to pick them up, but they still don’t seem to have any use.

Is this a bug, or did I miss something? Here is the link for the items https://ibb.co/PzgNSx08