When Wilson disappears for 3 hours where do you think he might have gone?
Obviously, Fitzgerald wanted for every reader to develop his/her own interpretation of Wilson's actions and movements during that period of time. Based on the events of the previous few days, it is likely that George Wilson spent some of that time investigating the identity of the owner of the "yellow car" that had struck and killed Myrtle. Since "no garage man who had seen him ever came forward," we have to assume he used other means of establishing that identity. Perhaps he found connections with some of the businesses frequented by Gatsby's servants on his behalf. Perhaps he talked with people in Port Roosevelt or Gad's Hill who could report to him on times when they had seen a yellow sports car in the area and had been able to describe the driver. Perhaps George had actually been working with an investigator to trace the activities of Myrtle, and had been able to learn Gatsby's identity from that individual.
What we do not know in Chapter VIII about Wilson’s whereabouts, we learn in Chapter IX. Tom tells Nick that Wilson came to East Egg and while there Tom tells Wilson that it was Gatsby’s car that killed Myrtle.
The police suspect that Wilson has spent the time trying to track down the owner of the car that ran down his wife. We know that Wilson believes his wife was not killed accidentally. He tells Michaelis that he suspects the owner of the car intended to kill Myrtle, saying,
“He murdered her.”
When tracking down Gatsby, Wilson is planning to exact revenge. He seems to believe that in doing so he is doing God’s will.
During the three hours that the police cannot account for, Wilson goes to East Egg and confronts Tom, who sees that Wilson is unstable and dangerous. Tom tells Nick that he saved himself and saved Daisy too by informing Wilson that it was Gatsby’s car that killed Myrtle. Nick realizes that Tom understood what would happen to Gatsby next. Wilson, however, is unaware of the truth (that Daisy was driving and that Tom was the one having an affair with his wife).
"[Wilson’s] faith in Tom makes him believe what Buchanan says, which, in turn, causes him to murder Gatsby and then commit suicide" (eNotes).
Thus in a way Tom kills both Gatsby and Wilson, two men that were his rivals in one way or another.
Wilson then becomes a tool of Tom in those three hours, although he believes he is a tool of God's retribution.