The Stoke defender has not played for his country for three years after falling out with previous boss John Toshack.
Unlike other players to have crossed Toshack, Collins did not officially announce his retirement from international football but he feared his chances of playing at that level again may have gone.
But Toshack's departure last month offered hope and Flynn, who has been put in charge for the Euro 2012 qualifiers against Bulgaria and Switzerland over the next week, was quick to get in touch.
Flynn, who is hoping to impress enough to earn the job permanently, visited Collins at Stoke and last week named the 30-year-old in his squad for the forthcoming fixtures.
The former Sunderland player, who has just seven caps to his name, said: "It is good to be back, it's been a while.
"I had a chat with Brian last week, he came to see how things lay.
"He asked me if I'd retired and I said I hadn't. He asked if I'd come back and I said, 'Of course I would'. I was delighted he asked me.
"Things went on in the past but we have moved on from that.
"I've missed it. Having weekends off watching games and not being part of it is not what you want.
"It's great to come back and hopefully be part of the team that qualifies for a major tournament."
Friday's clash against Bulgaria at the Cardiff City Stadium offers Collins the chance to pick up his international career against the team who were also the last international opponent he faced.
Collins faced Bulgaria in a friendly in August 2007 but then withdrew from the following month's Euro 2008 qualifiers against Germany and Slovakia.
He insisted he needed to work on his fitness at Sunderland but a row erupted and he was never selected by Toshack again.
Wales are now trying to qualify for another European Championship and, despite losing their Group G opener in Montenegro last month, Collins feels the squad is good enough to challenge.
He said: "We have had two good training sessions and it has been bright.
"We have one or two faces we would like here but we have some good young players.
"Aaron (Ramsey) is still out with a broken leg but Gareth (Bale) has become a top player and there is other great talent coming through. There is good potential.
"We have got two games now that will make or break us in the group.
"If we can come out of Friday's game on top that will give us a boost going to Tuesday night's game in Basle."
Collins has warranted his recall for his solid performances in Stoke's positive start in the Premier League.
The Potters are seventh in the table heading into the international break and Collins is enjoying life at the Britannia Stadium under another Welshman in Tony Pulis. Collins, who began his career at hometown Chester, joined Stoke in a £2.75million deal last year.
He said: "I'm enjoying my football. We've gone on a bit of a run at Stoke and are five unbeaten.
"It's going really well and that builds confidence.
"The gaffer is building a strong squad and some players are going to be unhappy when they get left out.
"The club have had two solid seasons in the Premier League and now looking to push into the top half.
"We are looking to build on the previous year each year and some silverware to go with it would be nice."