The 32-year-old Magpies skipper became the second Newcastle player to collect a treble in the competition after Tino Asprilla's performance against Barcelona in 1997.
But it was not the Colombian he needed to speak to after inflicting a one-man demolition job on Bayer Leverkusen.
Shearer has had to put up with some good-natured ribbing over the years from his former team-mate Rob Lee, who scored a headed hat-trick against Royal Antwerp in the 1994 UEFA Cup, and one-time strike- partner Mike Newell, who achieved the feat inside nine minutes in the Champions League with Blackburn.
Newell, now manager of Third Division leaders Hartlepool, was in the crowd at St James' Park on Wednesday night to see the former England skipper take his tally for the season to 21.
And while Lee was guaranteed a phonecall, Shearer headed for the players' bar to seek out his old sidekick in person.
"Mike has always gone on and on in the past about how he had scored a hat-trick in the Champions League and I hadn't," he said.
"Well, he can't throw that at me anymore. He was watching from the stands so we'll just have to see what he says now.
Remarkably, Shearer's first goal on the night a spectacular diving header from a Gary Speed cross was his first from open play in the competition, although he insisted that personal milestones did not come into his thinking.
Shearer's contribution means that United remain very much in the competition, but they will head for Inter Milan on March 11 knowing their dream could be over if they do not win at the San Siro.
That would cap another amazing comeback, perhaps even more unlikely than that which they staged to make their way into the second phase.