It is understood the pair had words after the Meads Cup semifinal clash between Wanganui and South Canterbury at Timaru on October 21.
Matthews' team were favourites to book a cup final spot that day, but Wanganui upset the odds with a 29-24 win - with Madams a prominent figure - and went on to claim a third successive Meads Cup title.
Yesterday, the 27-year-old said he was no wiser about what had caused him to be withdrawn.
"It's all quiet now. I dont know what the go is ... I dont know why yet," he said, still disappointed at being denied his New Zealand debut.
Last Monday, the Madams family received a phone call from Matthews, and he was out of the Heartland squad before they assembled in Timaru next day.
Madams and his father John attended a meeting with Wanganui Rugby Union chief executive Bridget Belsham to discuss the position on Thursday, but there has been no statement from the Wanganui union.
Approached by the Chronicle, Matthews said: "I've been told by NZ Rugby, no comment. I'm sorry."
The New Zealand Rugby Union was approached for a statement last Thursday and again yesterday, but media manger Juli Clausen gave no explanation and said they were still working through process requirements.
Wanganui team manager Chris Back, who was in Timaru last Saturday with the NZ Marist team, likewise deferred comment to the NZRU, although he phoned the Madams household last week to have a long talk to the family.
Yesterday Madams - known as a tough, aggressive player who sometimes likes to wind up the opposition - said he was looking for an official statement from the NZRU.
The lock forward was nominated for the Heartland squad by his Wanganui coaches Jason Caskey and Jason Hamlin.
- Late yesterday, NZ Rugby issued this statement:
"Sam Madams was removed from the New Zealand Heartland XV squad following discussion with Head Coach Barry Matthews, prior to the squads assembly.
"He was replaced by Everard Reid - one of two replacement players for the squad.
"There is nothing further to add."