I didn't see roots in that pic, just what looked like it was actually just some needles that got stuck in there (a bit of branch). For it to have been "growing", it would have had to have had roots.. and they should have had the entire specimen available for study (they seemingly don't)..
My guess is that he some how breathed in a bit of tree.. while hiking? playing in the woods? doing something he shouldn't have been so he "just can't remember"? but I seriously doubt it was a "seed" that germinated, sprouted roots, and turned into "just a tip of a sprig" since that's not how trees grow.