Is Fawkes the misshapen bird mentioned on page 722 of Deathly Hallows?

It would make sense if Harry really did see a phoenix fly into the flames of Dumbledore's tomb. He would have been encased in the stone and released when Voldemort cracked it open. Voldemort could have controlled him using dark magic. Does anyone else agree? Also, what happened to the tomb during the time when Voldemort opened the tomb and when he was defeated? Was Dumbledore's body simply left visible on the ground?