Dummett's hopes of returning to Paisley appeared to have been dashed last week but Newcastle finally allowed the left-back to return on the final day of the transfer window.
However, since Dummett left early this month Saints have beaten Celtic to reach the Scottish Communities League Cup final and followed that with a 2-1 SPL win over high-flying Inverness.
And Dummett knows he cannot expect to walk back in for tomorrow's William Hill Scottish Cup fifth-round clash against St Johnstone at St Mirren Park.
Dummett said: "Some players will probably go through their career without playing in a cup final and I'm only 21.
"I'm desperate to get back in but Graham Carey has been playing left-back and I can't expect to come straight back in the team. He has done a brilliant job.
"But that's what is good about the team, having players that can play in different positions and there is going to be a fight for places and that can only help St Mirren get better results and climb up the table."
Dummett made 19 appearances in his first spell in Paisley and then made his first-team debut as a half-time substitute in Newcastle's 2-0 FA Cup defeat by Brighton.
But he was always keen to return to Scotland.
"I'm very happy because I came here and played a lot games," he said.
"When I went back to Newcastle I played 45 minutes for the first team and I haven't played a reserve game.
"I feel playing week in, week out is the better alternative to progress my career.
"A lot of people do think it's not the best league but I can assure any young player that they can come here and improve.
"I've played Celtic two or three times and they are in the last 16 of the Champions League. This league is a good league."
Dummett feels his improvement was recognised when Alan Pardew handed him his Brighton run-out.
"He didn't have to put me on in that game, there were a couple of other players on the bench that I thought might have got on ahead of me," he said.
"He showed faith to put me on there. Maybe he had reports back saying I had done well here.
"I know it wasn't a good result but I don't think I did myself any harm coming on in that game."
Dummett and fellow loan player Conor Newton could come up against Newcastle team-mate Mehdi Abeid after the midfielder moved to Perth on transfer deadline day.
Dummett said: "He's a good player. Conor and I know him well and we're looking forward to playing against him
"He has been brought in from France but he has been at Newcastle for two years now."
Newton's arrival this month, coupled with the return to fitness of Kenny McLean, saw Saints boss Danny Lennon agree to loan midfielder Jon Robertson back to Cowdenbeath.
Lennon said: "He is out for a month and by no means are we looking to chase Jon away.
"He has still got a big, big part to play. I told them if there was any doubt, 1%, don't go.
"Where we are sitting in terms of depth of the squad, he sees himself slightly on the outside, but we know how quickly that can change.
"Jon is going there for the right reasons, to get game time, and he is developing at the pace we thought he would.
"In the absence of Kenny McLean, he came in and did terrifically well."