I don't know what the significance was of the thread vis-a-vis the turtle at the end, or if that was a just scene showing all the various clues. They seemed to be connected to Mason, though. My wife's first comment about the thread was "does the mom do crochet" and that got me thinking about the turtle blanket, but on a relook, the blanket appears to be stitched in green, not blue.
Thanks for the link.