Can recall for sure but John rallied his will and forced Sinestro out of both him and his lantern ring. Sinestros' ghost then appeared to confront Guy when Guy got into the crypt to steal the yellow ring.
Guy defeated Sinestro's ghost and claimed the ring.
Next time I remember Sinestro returning was when the Guardians released him from the CPB to fight Hal.
As to Sinestro being dead, I think the better explanation is that he projected himself into the CPB as they were killing him. His body went into stasis and his essence was in the CPB.
The Guardians then stuck him back into his body to fight Hal and during all the explosions and smoke caused by the fight, Sinestro had Parallax make a Sinestro replica while Sinestro fled to Qward to slowly start building his own Corps.
Hal kills the fake and is taken over by Parallax.
As I recall, in Rebirth it was stated that the Corps never actually executed Sinestro, they simply imprisoned him inside the CPB. All ghosts of Sinestro were Parallax constructs. Maybe that still works for driving John mad. When the Guardians resurrected Sinestro in Rebirth that was another construct. How could they not know? When Hal cracked open the CPB to steal its power, Sinestro escaped and hid out for 10 years (real time). When Hal/Spectre encountered Sinestro's soul that was yet another construct, I guess.
I don't like these retcons when they state that what you saw in the original comic never happened, i.e. the Corps deciding to execute Sin. Johns likes to do that, like in Teen Titans when he suddenly announces that Kon-El is a clone of Superman and Luthor. He just invalidated 10 years of comics!