SO lets study the Anakin Burn face pic,
Obi must see him in this picture becos they wouldnt randomly show him with a burnt face, So what really does happen in that shot, In Anakin falling or Busting out of the fire or what ever hes coming out at him.
I think Anakins Bursting out of the Lava and Obi is walking away thinking hes dead and he just captures a gimpse of him bursting out of the lava as hes leaving on the ship. and Obi doesnt care about him anymore