Saints appealed for a spot-kick with 10 minutes to go when Nathaniel Clyne's cross hit Ryan Bertrand's arm but referee Mason decided it was accidental and waved away the vociferous appeals.
And the former Argentina defender told Sky Sports: "I thought we did enough to win the game. It didn't quite happen for us in the end although we lacked a clear edge towards the end of the match and it was also a clear penalty that did not go our way.
"Nathaniel Clyne told me it was a clear penalty, so it was a clear penalty that was not given.
"We feel hard done by because in the last few games we had decisions that
haven't gone our way and probably, if those decisions had gone our way as they should have, then we would have more points right now. The players did not deserve those calls.
"We started off really well and controlled most of the game over the 90 minutes that we played. We had around 70 per cent possession which says a lot.
"Overall, I'm happy with the way the team played but also disappointed with the number of chances created and we were not able to put the game to bed."
The point helped the south-coast club move three points clear of Newcastle in eighth position with just three games of the Premier League campaign remaining.