Raphael Varane twice appeared to be fouled in the penalty area during a first-half corner, first by a shirt -pull from Ivan Rakitic, and then by Clement Lenglet when he caught his French compatriot on the thigh with his studs.
Ramos told Movistar (h/t Goal's Joe Wright): "We saw them at the break and they look pretty clear. They're both penalties, but we can't change that now. VAR is here to help. It's bad luck. On another day, it'll be our turn to have a penalty that they don't check."
The Spanish Football Podcast observed the early controversy in the match, while AS provided images of both incidents:
The high challenge from Lenglet left its mark on Varane:
Real Madrid followed the lead of their captain, with the club's official website stating "neither referee nor VAR system saw two penalties on Varane."
Alejandro Jose Hernandez Hernandez, who officiated the game, did not consult the pitchside monitor to review either incident.
Real also had a VAR call go against them in the second half when Gareth Bale had the ball in the back of the net, but it was disallowed for an offside against Ferland Mendy.
It was a frustrating night for the visitors, who were dominant in the first half with 12 shots on goal.
Casemiro had a header cleared off the line by Gerard Pique, although Barca also had some excellent chances, too. Ramos had to intervene on the line to clear a goal-bound shot from Lionel Messi, and Jordi Alba failed to hit the target after the Argentinian had picked him out in space:
As football writer Dermot Corrigan observed, it has been some time since both sides failed to score against one another:
Ramos saw plenty of positives from Real's performance, though:
"We saw a great Real Madrid today, with a lot of personality, on a very tough pitch. We went to steal the ball, which helped us create many chances. There were few mistakes and that's the end result.
"We controlled the game quite well. We had more chances than them. It's not easy to get the ball off them. The strategy of pressing high worked well."
Real have now lost just twice in their last nine visits to the Camp Nou in all competitions.
Wednesday's draw means the two sides remain level on points after 17 matches. Their head-to-head record for this season is even, so Barca are ahead thanks to their marginally better goal difference.
Given there has been little to separate the two sides so far, the title could rest on the second Clasico of the campaign when Barca visit the Santiago Bernabeu on March 1.
Barcelona have won six of their last seven matches at the Bernabeu, so they perhaps have the edge in the title race.