Ernesto Valverde was left puzzled as to why a second-half penalty was awarded in Las Palmas' favour as Barcelona's lead at the top of La Liga was cut to five points.
Lionel Messi's free kick had given Barca the lead in Gran Canaria on Thursday when referee Mateu Lahoz awarded a spot kick to the home side just after the break.
It was the first penalty awarded against Barcelona in over two years -- since a game against Celta Vigo on Feb. 14, 2016 -- but there was confusion as to why it was given.
Even after the game, Barca's players claimed they hadn't been informed why it had been awarded, with a Lucas Digne handball or a Sergi Roberto pull on Matias Aguirregaray the two most likely possibilities.
Jonathan Calleri scored from the spot to earn his side a vital 1-1 draw in their fight against relegation.
"We don't know what the referee gave the penalty for," Valverde said in his postgame news conference. "In the dressing room, no one knows. We don't understand what he's blown for, it's unexplainable.
"Maybe when we see it on the television it will clear up what the decision was for. It was an invisible penalty. It did us a lot of damage -- for how it was given and the sensation it left us with.
"Las Palmas defended well, we tried to break them down but as the game progressed there was less rhythm and it got more and more difficult."
Speaking after his coach, Barcelona captain Andres Iniesta said he believed the penalty had been given for Digne's handball.
Valverde was also incensed by Lahoz's failure to spot a handball by Las Palmas goalkeeper Leandro Chichizola just before half-time, after he appeared to use his hand when outside of his area to stop Luis Suarez having a free run at goal, but was not penalised.
"I spoke with [Lahoz] at half-time," Valverde added. "It was a clear handball outside the area and he's not seen it. For me, it was clear, although I imagine it was different for [Las Palmas coach Paco] Jemez."
Barca, who remain unbeaten in the league this season through 26 games, are back in action on Sunday at Camp Nou against an Atletico Madrid who have closed the gap on the La Liga leaders.
Less than a month ago, Valverde's side were 11 points clear at the top but their advantage could be cut to just two points if they lose this weekend's top-of-the-table clash.
"The game against Atletico will be important for both teams," Valverde said. "We've got a bad taste in our mouths because of how we've drawn and because we could have won this game [against Las Palmas].
"But we're still top, Atletico are second. The gap's been reduced by two points, but we're motivated to win the game on Sunday."