"It was just the boys who were subs for the Slovakia game a couple of days earlier," he said, reflecting on his summons, along with four other members of the Scotland under-21 squad, to take part in a training match with the full team in October.
That Callum Paterson, Fraser Kerr, John Herron and Mark Beck were also involved validates the 19-year-old's assertion but, while Gordon Strachan's immediate focus was fixed on the impending World Cup qualifier against Croatia at Hampden, the national coach had given some attention to the left-back. He recalled Robertson as a member of the Queen's Park side who helped with a team-shaping session ahead of the qualifier against Wales last March, where he made an impressive contribution against Chris Burke - "Andy was inspirational; I thought he was terrific," said Strachan.
The Scotland manager's interest had intensified after watching the defender make his full Dundee United debut against Partick Thistle on the opening day of the SPFL season. The teenager was one to watch.
Now, after just 32 games as a full-time professional, Robertson is on the verge of making his international debut against Poland on Wednesday.
"I didn't expect it to happen so soon but I'm really looking forward to it," said Robertson, who joined up with the squad last night. "Last time, I was there as a 21s player so there was maybe no pressure on us but there's pressure every week playing for Dundee United so I'm sure I'll deal with it."
Robertson delivered another accomplished performance in United's comprehensive win over Hibernian on Friday evening before joining team-mates Paul Paton (Northern Ireland) and Curtis Good (Australia) in leaving to become part of their national sides for the first time.
"It will be a massive learning curve, playing with experienced pros like Darren Fletcher who has been through everything in the game," said Robertson. "I'm determined to enjoy it and, besides, it's easier playing with top players as I've found coming to United."
One experienced pro who will not feature against Poland is Grant Hanley. The Blackburn Rovers defender has had to withdraw from the squad because of a calf strain.
The Scotland and Wigan Athletic midfielder Shaun Maloney, meanwhile, will not be rushed back into action after six months out with a hip injury, although he has resumed full training after a period of rehabilitation in Colorado, USA.
"You need to make the player aware of where he is and the consequences of maybe coming back too early," said Uwe Rosler, the Wigan manager. "It's important everything is done right because the expectation from everyone - the player, me, the team and fans - will be enormous."