Founder member Sheehan had been missing from the recent American leg of their greatest hits tour.
In an exclusive interview with the
Sunday World before last night's performance at the SSE Arena, singer Danny O'Donoghue confirmed Mark had taken time out for family commitments.
"It's his story to tell, but yeah, I guess if I could paraphrase, his children needed a father and his wife needed a husband," Danny told me.
"He's been the engine of The Script for such a long time, [I told him] that 'if you want to take a bit of time out for your family you are more than welcome to, and I insist on you going and doing it'.
"He took a little bit of time off. You get refreshed, then you come back with a new zest for life. And I believe it was the best thing that could have happened for all of us.
"Me and Glen had to get on with it in the meantime. We did the American leg without him, but the second we all get back in the room again for the Irish tour you just sit there and you go 'there's the f**kin' magic!'"
Danny acknowledged there is extra pressure on band members who are juggling family life with the demands of touring.
He said: "I don't have kids. Mark does and Glen has a son, but the thing about this band is that we are there for each other. We are not here for personal gains.
"When my lung collapsed, the lads stood in for me. When I went through a load of s**t, the boys were doing interviews for me left, right and centre. That's what this band is…we are a band of brothers and we stick together no matter what.
"There was probably a bit of kerfuffle ... 'where is he, we need a statement'. He's just taking time out for his family. He's coming back when he feels he wants to come back and we're holding the fort up for him - it's no biggie.
"Anyone that has kids will understand that - and the ones that don't, won't."
Danny admitted he was nervous going back on stage after more than two years off the road.
"We did the first leg in America and, I'm not gonna lie, not having done anything in two and a half years, it's like you never did it in the first place," he told me.
"I was so nervous. It's the 'best of' and it's nearly 14 years of lyrics to remember. But it was such a release of emotion, and I mean that from my point of view.
"We had stopped mid-tour [due to the pandemic] and went into a house for nearly 18 months and then didn't know if we were ever going to get to play again, if we were able to get to hang out again.
"Just to get back out rehearsing again was something, and then to fill a place full of people with no masks - we're on stage and we're all singing, it felt like normality again.
"I went to a football match in Wembley and it was really weird being among 40,000 people, because up to then it had just been me and my missus [in lockdown] for such a long time.
"I remember the hair on my neck started to stand up when they all started chanting and singing. I realised I had missed it so much and it was such an emotional moment.
"So it gives a new feeling to doing shows again. I swear it's a drug to me. I'm just so excited to start playing, and we are kind of catching a wave that not a lot of bands have the privilege to do as well, to start playing for massive crowds.
"Although we'd done America, I just can't wait to play these Irish gigs, just being on home soil.
"We were chatting with Ed Sheeran two days ago and, of course, he just recently played Croke Park. For a lot of people, that would have been the first big show that people were allowed back out to again.
"He said there was a touch of magic in the air getting this wave of people finally being back out and able to touch each other again, having a few drinks, singing their heads off and having the time if their lives. So we're looking forward to experiencing that again in Ireland."
The Script play Belfast again tonight, Dublin's 3Arena from June 14-16 inclusive and Cork's Musgrave Park on June 19. Extra tickets are now available through Ticketmaster.