Even the Ghibli Music Collection torrent on BakaBT (
http://bakabt.me/142405-ghibli-music-collection-flac.html) doesn't have that Treasure Hunting soundtrack. They have the two you are sharing, though, also in FLAC. But thanks anyway, I haven't listened to any Ghibli Musuem soundtrack yet!! Thank you for finding these obscure links!! :'D
Most Studio Ghibli Musuem soundtracks can only be purchased at the museum's gift shop.
http://www.nausicaa.net/wiki/Studio_Ghibli_Museum_%28soundtracks%29
^^"