Answer:
The "three" hours disappearance of George Wilson was due to the fact that he had gone to East Egg, to Tom Buchanan to tell him about the driver of the car that killed his wife Myrtle Wilson.
Step-by-step explanation:
George Wilson was the owner of the run down auto repair shop where he lived with his wife Myrtle. It was this woman who Tom Buchanan was having an affair with in F. Scott Fitzgerald's "The Great Gatsby".
In Chapter VIII, after the devastating accident that killed Myrtle, George had decided to find out the driver of the car who had run over his wife. The "three hours" that Wilson wasn't available, he had actually gone to Tom Buchanan's place and told him about the car and its driver, who he believed to be his wife's killer. Tom, in turn, told him that it was Jay Gatsby's car and it was him who had run over Myrtle, which set in motion the whole scene making George try to kill Jay but ended getting killed instead.