Diaz missed Liverpool’s 3-0 win over Nottingham Forest last weekend after returning to Colombia following news that his parents had been kidnapped, but he returned to training this week and came off the bench to earn the Reds a point at Kenilworth Road.
The forward’s mother has been released but he is still waiting for news on his father. After scoring, Diaz lifted up his shirt to reveal a white T-shirt which read ‘libertad para papa’ – ‘freedom for my father’.
Liverpool boss Klopp lauded the player after his header looped over Hatters goalkeeper Thomas Kaminski to cancel out Tahith Chong’s earlier strike.
“It’s wonderful, it’s emotional and it’s fantastic,” Klopp said.
“We wanted to give him the chance to be a little bit distracted from things. He cannot do anything, he’s waiting all the time and so he trained a few times and he was in a good mood, which is good.
“The signs from Colombia are positive and optimistic but not the one thing we want to hear.
“He brings the quality with the 15-20 minutes he played.
“I think not many people (can) imagine what he has going on now – even us, we are close to him of course, we are supporting him, we feel his pain, but for him it is a different level.
“Football sometimes in dark moments can bring joy to people, can bring joy to somebody who is struggling, and I think football is bringing a slice of joy to him at this time.
“We are together with him, for whatever he needs. He came, trained, came to the game, scored a fantastic goal for us that was really important and we are with him 100 per cent.”
The hosts stifled Liverpool in the first half.
And German boss Klopp highlighted his frustration with a lack of counter-pressing which he felt was “personal”.
He added: “What I didn’t like was that in the first half we had no counter-pressing.
“That’s something I take personally and I’ve told the boys that’s really not OK.
“I told them at half-time to be patient and that if they could add counter-pressing into the play then that would be really helpful.”
Luton almost played the perfect game, only to concede late on.
And manager Rob Edwards felt pride at full-time after his team’s efforts gave them an important point in their survival bid.
“My overriding feeling is pride,” Edwards said. “Of course we wanted to win the game but maybe they would have felt hard done by if we had won that.
“We had a plan and the players committed to it and we got close. The feeling is pride.
“The players gave everything.”