Television replays showed Hamilton's shot leading off the fourth inning against the Baltimore Orioles cleared the 14-foot fence in left before ricocheting back onto the field. The ball hit a support beam that connects the left-field scoreboard to the wall.
Hamilton was stranded after the next three hitters were retired, leaving the Rangers trailing, 2-1. Texas came back and won, 4-3, on Nelson Cruz's sacrifice fly in the bottom of the ninth.
Rangers manager Ron Washington disputed the call with second-base umpire Doug Eddings.
"The umpire told me it hit the pad," Washington said. "He saw background with white ball and pad. So if he saw background with white ball and pad, I didn't ask for a replay."
DeMuth indicated he would have denied a request for a review had Washington asked for one.
"[Washington] can ask all he wants, but [a review] is up to the crew chief," DeMuth told a pool reporter after the game. "I have to have trust in my crew, and my crew member was 100 percent sure of that call."
He wound up regretting the decision not to look at the replay.
"Obviously I'm wrong," DeMuth said. "It should have been a home run. To see this right now is very upsetting because this is a great tool that Major League Baseball has given me, has given crew chiefs, has given umpires. I can see that I did not use that tool."
It would have been Hamilton's second home run in the game after he hit a solo shot in the second inning.
"It's a tough call, especially from down on the field," said Hamilton, who has eight home runs this year. "What is that, three or four inches just over the pad and bounce back? [Orioles second baseman Ty] Wigginton told me it hit the pad, the third-base coach thought it hit the pad, so it is what it is."
The Associated Press contributed information to this report.