Lonergan was in attendance along with fellow first-team stars Hadi Sacko and Ronaldo Vieira as the Whites beat Forest 5-1, thanks to goals from Tom Pearce, Paudie O'Connor, Oriol Rey, Alex Machuca and Adrian Balboa all scored.
Leeds posted a picture of the first-team trio on Twitter at Thorp Arch as they watched Leeds' stars of tomorrow shine at the Whites' training ground, as Jay-Roy Grot, Pascal Struijk and Bailey Peacock-Farrell also impressed.
Lonergan, who is currently playing second-fiddle to Felix Wiedwald in Leeds first team, posted on his Twitter account stating the victory was a "great 5-1 win".
Well played today lads, great 5-1 win! https://t.co/yCOshSIukE— Andrew Lonergan (@lonners24) February 9, 2018
The veteran goalkeeper, who almost joined Championship side Sunderland on deadline day, is expected to remain on the bench at Bramall Lane on Saturday as Leeds travel to face Yorkshire rivals Sheffield United.
In Paul Heckingbottom's first game in charge, it remains to be seen what kind of side the former Barnsley manager fields as he looks to end Leeds' run of seven league and cup matches without a win.