McFadzean's goal in the sixth minute of time added on secured a 2-1 win against Nottingham Forest and completed a superb comeback after Viktor Gyokeres had equalised in the 81st minute to cancel out Lyle Taylor's first-half effort for the visitors.
It was the Sky Blues' first game back at the Coventry Building Society Arena following two years as tenants at Birmingham City's St Andrews following a dispute between the club's owners Sisu and rugby union club Wasps, who will now share the stadium with Robins' men.
A delighted Robins said: "It's brilliant to be back and it was a brilliant atmosphere.
"I've got to thank the supporters because they were absolutely magnificent helping us to get back into the game.
"If you ask any supporter, I'm sure they would tell you it's been a really emotional day for everyone and that might have played a part in our first-half performance because we didn't do ourselves justice.
"But, when Kyle gets on the end of a free-kick to score a 96th-minute goal, I don't think there could have been a better way to end the day for our supporters and players."
For long periods, however, the visitors had looked like they could be party poopers, with Robins adding: "Forest are a well-coached team but they've had Covid issues, as we have done, over the summer and I think that was always going to have an impact and both teams were never going to be ready to perform at their highest level.
"We allowed them too much space in the first half, but we then took the game by the scruff of the neck.
"The introductions of Tyler (Walker) and Jodi (Jones) made a difference and made a difference for Viktor (Gyokeres), who hadn't had much joy but stuck at it and got his reward with the equaliser."
Forest boss Chris Hughton admitted positive Covid cases and self-isolating periods had taken their toll on his squad during a disrupted pre-season.
He said: "For 65 minutes I thought we were good and restricted a team playing at home with an offensive structure to minimal chances.
"We scored a very good goal, but I think we became tired and, when your opponents are in the ascendancy, you have to make good decisions and it looked too much for us in the end.
"We've had a challenging time with Covid. A lot of players haven't been able to train and we had to call two games off and that can show at the end of games, but these are the challenges you have to work around."
Hughton was buoyed by Taylor's goal, though, with the former Charlton striker having finished last season with just one goal from his last 29 outings.
"He showed good urgency to get to the back post and score and his overall game was good as well. Let's hope there's more to come from him" the former Newcastle boss added.