Identified the Mosaic tile from Western Approach that doesn't appear in Skyhold

In all my playthroughs I have suffered from this bug: one of the Archdemon mosaic pieces (found in the Western Approach) does not show up in Skyhold once it's found. I have identified which one is bugged: it is the one you find in the cave that opens up once you have completed all 3 astrarium puzzles in the area. It is just east of one of the 4 campsites in the Western Approach. It is a small bug, but annoying - I hope this can be fixed in a next patch.