The This Morning presenter joked on social media that the ITV skating show is "actually very good", as he watched from the comfort of his own sofa.
The 44-year-old In For A Penny presenter exclaimed to Willoughby, 40: "Can you believe it's 16 years since we worked together on kids TV?!"
She replied: "I know! We're grownups now!"
The duo co-presented Stephen and Holly's Saturday Showdown on Saturday morning's on ITV from 2004 to 2006.
Willoughby started the show by announcing that Schofield was missing hosting the skating show for the first time ever in 14 series as he was isolating at home.
She said: "We know he's watching at home, sending you lots of love Phil."
Schofield posted a clip of Willoughby and Mulhern on Instagram, saying: "Well this is an experience I never expected. I'm loving watching with a G&T. Enjoy Stephen Mulhern."
He added: "Just discovered this show. It's actually very good. Cheers."
Earlier Schofield, 59, revealed he had produced a positive lateral flow result for the sixth day running, meaning he will miss This Morning with Willoughby on Monday morning.
He shared his test on social media joking: "This really is the day that keeps on giving!! Sorry @ThisMorning @HollyWilloughby."
Schofield - who is fully vaccinated - first revealed he had tested positive for coronavirus on social media on Monday night (31 January).
Humes had been co-presenting the ITV morning show for the past two weeks while Willoughby took a leave of absence to film new survival show Wim Hof’s Superstar Survival, featuring The Iceman.
But she is due to return tomorrow.
Government guidelines for those who have tested positive with coronavirus now state that you can leave the house after five full days of self-isolation if you test negative on day five and say six.
Schofield appeared via video-link on This Morning and revealed: "I'm fine. I haven't even got a sore throat now. I've sneezed twice, and that's it! I've got a slight temperature.
"This is not what I expected, I've got to say."
Meanwhile, Olympic BMX rider Kye Whyte returned to the ice after taking a week off on medical advice, due to an injury he had suffered to his knee in training.
Last year's Dancing On Ice suffered a record number of celebrity drop-outs, with five celebrities forced to leave the cast over injury and testing positive for COVID, and a number of the pro skaters also injured.
Watch: Dancing On Ice audience member's screams distract viewers