I found the wooden mask and the dragon shrine, I brought the wooden mask back to breezehome and set it on a table. It's now gone. According to some sources, I've heard it will despawn if left in the open (even in your home). If this is the case, this definitely needs to get fixed. A unique item like that should not be despawning particularly in your own home. It also appears the mask doesn't respawn back at the Labyrinthian Mound.

And before anyone asks it, yes I've searched all around as it may have been knocked off the table.