Martin O'Neill's side fell to a 3-0 defeat in Bordeaux on Saturday, with an Axel Witsel header and Romelu Lukaku's double securing maximum points for Belgium.
However, prior to Lukaku's opening goal, Long had claims for a penalty kick denied after he was on the receiving end of treatment from Thomas Vermaelen and Toby Alderweireld
"I can’t really say what I really want to say because I’ll probably get myself in trouble," the Southampton striker told 98 FM after the game.
"It’s just disappointing, anywhere else on the pitch you might get a free-kick. The fact that they broke and scored as well makes it a little bit harder to take."
The former Cork City attacker added: "He (referee) obviously thought there was nothing there. He must have thought I was diving or something.
"I can’t really say what he was thinking because the pictures speak for themselves."