During the first leg in Belfast, Hategan gave the visitors a spot kick after believing that Corry Evans had handled the ball, only for replays to show that contact had been made with the player's shoulder.
The converted penalty would prove to be the only goal of the two-legged tie, and Hategan has acknowledged that the decision has cost him a place among the officials at this summer's World Cup.
Hategan told reporters in Romania: "It was a sad and unpleasant moment for me, sad because I made that mistake.
"Unfortunately I'm not among the 36, but I'll see if I'm going to be a video referee. Surely it has had a big influence and what happened in the playoff game. It's not a secret and I'm not hiding behind words.
"In our world, the referees are the same as the goalkeepers - everyone sees the mistake."