Some thoughts from Lloyd Davis, book editor extraordinaire and secretary of the Society for International Hockey Research:
I doubt that he was drafted by the Junior B Detroit Jr. Red Wings. It was still the sponsorship era, so I don’t think the OHA had drafts. Otherwise, a guy like Paul Henderson wouldn’t have had to weigh three offers in 1960. (He tells the story that he ended up choosing Boston, where he figured he’d play the most, but on the way to Niagara Falls to sign his C form and try out for the Flyers, he got intercepted by the GM in Hamilton, where the Red Wings had their junior team.) It was still the era when Boston would sponsor the entire Parry Sound minor hockey system in order to secure the rights to Orr, something Detroit did in Stratford to get Nick Libbett.
A move from Montreal to Detroit would’ve raised residency issues. In 1968, when Marcel Dionne left the Drummondville Rangers to play in St. Catharines, family members had to move with him to satisfy the OHA that he was in fact living in Ontario. Even in the ’70s, when Gretzky left Brantford to play Junior B for the Toronto/Seneca Nationals, there was a legal wrangle with the sanctioning bodies. So it’s highly unlikely that a Junior B team in Detroit drafted Nadon. If the NHL Red Wings had any interest in him, they’d likely have secured his rights and put him on the St. Jerome Junior A team.