"Your boys were the best team we've played this season," Grealish could be heard telling the 51-year-old, who was performing punditry duties for a television broadcaster. Or words to that effect.
It was a snatched conversation, between two Premier League-bound professionals whose teams have taken different routes into the top-flight.
But Wilder, whose United side plotted the shortest possible course by securing automatic promotion from the Championship, might have reason to curse Villa's victory over Derby County in the Wembley showpiece. Despite, as his demeanor around Grealish and later Dean Smith confirmed, the respect he has for the Midlands club.
Although Smith has yet to outline his plans for this summer's transfer market, other than suggesting Grealish will remain at Villa Park, there are suspicions they will include a bid for Neal Maupay who he coached at his previous club Brentford. Wilder also admires the Frenchman, who scored 28 goals last term. But if he decides to submit a concrete bid, the chances are Wilder will find himself going head to head with Smith in a battle every bit as fierce as February's 3-3 draw between their two sides in the West Midlands.
After leaving west London to take charge of Villa in October, Smith was reportedly considering a bid for the Frenchman during the January window. Although that failed to materialise - perhaps, in part, to the reported £15m asking price - Maupay admitted during an interview before Christmas he would be tempted to resurrect their partnership should the opportunity arise.
"I have a really, really good relationship with Dean, Maupay told The Independent. "So obviously if one day he calls me and says ‘Neal, I need you in my team’ I would consider it.
"But at this moment I can’t be focused on other things than Brentford. Obviously, I really liked working for him, so if one day he wants to bring me to Villa or wherever I would listen to him because he has done a lot of good things for me."
Of course, should they test the water themselves, United could offer Maupay plenty too. The sheer volume of chances they create, coupled with the ease with which ex-Brentford players seem to settle in Wilder's system, are bound to prove appealing. Jack O'Connell and John Egan, Maupay's former colleague in the capital, both performed influential roles as United finished second in the table; three places and 13 points above Villa.
But with time being of the essence, Wilder will be keen to avoid being dragged into recruitment battles he fears United are unlikely to win. There is nothing more frustrating, or potentially damaging, than chasing a target only to see them eventually move elsewhere. After, as often proves to be the case, alternative options have also been snapped-up by rival clubs.
Wilder has been there before, most notably during the last two summer windows. Despite still going on to achieve great success, he will not want to find himself in the same situation again.
Although he prefers to do his business in private - many of the names recently linked with United do not feature on their wanted list - Wilder is known to be chasing at least two centre-forwards and an attacking midfielder.
With Gary Madine, Hogan and Kieran Dowell leaving Bramall Lane at the end of their loans, United are short of numbers at the top end of the pitch. Given the physical demands placed on the wing-backs in their 3-5-2 system, providing extra back-up Enda Stevens, George Baldock and Kieron Freeman would also appear wise.
Goalkeeper Dean Henderson is likely to return for a second spell on loan after United held positive talks with his parent club Manchester United.
Together with Dowell, the Everton midfielder, Henderson has been named in the England under-21 squad which will contest the UEFA U21 Championships in Italy and San Marino this summer. Wilder would prefer to reach a binding agreement - or at least a firm undertaking from Old Trafford about Henderson's destination next term - before the Young Lions depart next month.