The decision, which came after the TMO had reviewed the incident for five minutes, meant Gloucester ran out 29-23 winners.
Betty said: "We're all gutted to be honest. Every player is devastated with the decision and it's hard to take a loss like that.
"We worked really hard and we did enough to win. But we're just not getting the luck."
It was not the first time this season Warriors had been denied victory in the final stages of the match and Betty admits it is painful for the players to accept.
He continued: "It's been happening too many times. We do enough to win the game but give it away in the final minute.
"It's partly down to us and partly down to some decisions by referees. But it's one of those things and we'll keep working hard and hope we make our own luck."
Warriors picked up a losing bonus point to move eight points clear of Sale Sharks at the bottom of the table.
And, according to Betty, players will use the weekend to get over the latest setback before turning their attention to next Friday's clash with London Wasps at Sixways.
He added: "We've got the weekend to think about the Gloucester game and then we'll come in next week ready to face Wasps.
"I don't think anyone will ever question our heart and our commitment. All you can do is give your all and hopefully things will start to go our way and we'll be on the way up."