It just did not compute. Fit footballers newly turned 20 who have been operating in a bubble for weeks aren’t supposed to contract the disease.
Gilmour is himself still mystified and while it’s not a case of all’s well that ends well – deprived of his talents in the middle of the park at Hampden against Croatia, Scotland were eliminated from Euro 2020 – life has moved on to an extent. The Scots have their sights set on another major finals.
Gilmour has now belatedly made his Hampden bow, in Saturday’s night’s 1-0 Group F win over Moldova. The victory keeps Scotland in the hunt for World Cup qualification. Their next must-win game comes in the Ernst-Happel stadion tomorrow when Steve Clarke’s side seek to effectively remove Austria from the qualifying equation.
It’s another important few days in the life of someone who has quickly developed into Scotland’s pivotal player – two man of the match awards in three competitive games underlines this status. It was good to stand and hear the midfielder reflect on these dizzying last few months as he clutched his boots on the Hampden trackside after Saturday’s game.
Behind him lay the pitch on which he had just left a distinguished tread and all being well, will continue to do so for many years to come.
“To walk out at Hampden for the first time was a special night,” he said. “It is one I will remember. My family were here watching so overall it was a good night.
“I want to represent my country,” he added. “I love coming away here. They are a good group of boys and we have a good manager and we are looking to go to the World Cup. We want to do something special.
“It is always good hearing them (the fans) shout you on and cheer you on. They were loud tonight and helped the team push through.”
They would have been even louder in their acclaim of him had Gilmour managed to steer an effort inside the post rather than just past it in the second half after a one-two with full debutant Kevin Nisbet.
“I know!” he said. “I am still waiting for that first goal. I honestly thought I had put it in the net . . . then I saw it go past the post. I am gutted. Hopefully it comes soon – hopefully next week!”
Both Gilmour and 19-year-old Nathan Patterson caught the eye and it seems likely they will start in Vienna tomorrow with Scotland required to be on the front foot against their hosts. “I thought Nath played really well,” said Gilmour. “He and I have come through the full youth system with Scotland and also Rangers together since we were young so it was good to play alongside him again and make our debuts at home together.”
Gilmour would have done so earlier of course if not for that Covid positive test. He has put it behind him now but what a bitter blow for one so young to go from the high of Wembley, where he starred in Scotland’s 0-0 draw with England, to missing out against Croatia in the next game where he would have pitted his wits against Luka Modric.
"I felt fine but when I got told I was gutted,” he recalled. “I was asking to do more tests but they all came back positive so it wasn't good. I had to watch the Croatia game, sitting by myself. I was cheering them on but I was gutted for the lads.
"It just made me hungrier to come back here and prove why we should be going to the World Cup.”
There was one consolation. If you are going to have to self-isolate for ten days then doing so when there is a major football championship finals on television nearly every day seems the optimum time.
"It was a long 10 days but there was football on the TV so I got to watch that,” he said. “That was the only positive.
“I wasn't allowed to train. I couldn't do anything. I just had to stay in my room and watch TV. That was it.
"From the high of Wembley to a low that quickly was hard. I was gutted but I was happy I got to go to the Euros, especially after it was the first time Scotland had qualified in so long. It was an amazing experience.”
Then there was the little matter of the repercussions for Chelsea teammates Mason Mount and Ben Chilwell, who were deemed to have been close contacts of Gilmour because they spent time speaking together after the final whistle at Wembley. It meant the pair missing England’s last group game against Czech Republic.
Part of his self-isolation was spent chatting on the phone to them. Gilmour could only apologise though he had nothing to apologise for. To this day he does not know where he contracted Covid from. “Honestly, I don't have a clue,” he said. “I still think to myself everyday, 'How have I managed to catch it?’
“They (Mount and Chilwell) were negative but they had to stick to the rules so it is what it is.
“I got a couple of messages from the boys in the team while I was isolating saying they were gutted I was missing out. I just wished them all the best in the last game.
"I just wanted them to do well against Croatia but sadly it wasn't to be.”