The Reds added a sixth Champions League title to their cabinet with a win against Tottenham earlier this month.
Mohamed Salah and Divock Origi gave Liverpool their first European honour since 2005.
That title came in a stunning comeback against AC Milan, which was dubbed the “Miracle of Istanbul”.
Steven Gerrard led his side to a 3-3 draw, winning on penalties, after going 3-0 down at half time.
One star to miss out on the win was Warnock, who made 30 appearances for the Reds that season.
And the 37-year-old told Stadium Astro the brutal way he was told he did not have a place in the squad.
Speaking on League of Legends, Warnock said: “We were due to fly to Istanbul two days before the game.
“So every time you walked into the changing room after training, the squad list would be up.”
Warnock’s revelation comes as:
“The players would run up to it because it had 18 players – the starting 11 and subs.
“It went up and I was in the squad, so I was straight on the phone to family.
“It was just an amazing feeling to know you were going to the club’s biggest game in their history and be part of that.”
But Warnock soon found out it was not meant to be.
“About three hours later, I got a phone call from the assistant manager,” the former Reds man added.
“He said ‘we’d made a mistake on the squad list and I wasn’t in it’.
“That was tough to take because it wasn’t the manager who rang me.
“So I lost all respect for Rafa there and then.
“For him not to pick up the phone for the biggest game of the season, I lost all respect.”
The 41-year-old went on to say how much work he had put into getting to Istanbul.
Warnock continued: “There was a two-week period after the season finished to the Champions League final.
“We were in pretty much every day, getting ready.
“I played in the last home game of the season against Aston Villa.
“I played well in the game but said to myself ‘I need to train well now for two weeks and prove I can get into this squad’.
“I’d been in pretty much every squad for most of the season.”
It comes as Reds fans have labelled Manchester United’s transfer plan “desperate”.
