Having lived in rural Alberta during that same period of time, I’d also be highly doubtful Sam was connected to a bike gang considering his aboriginal heritage. Since he wasn’t reported missing by his family I’d guess he was raised by others in some sort of loose caregiver arrangement. Then as an adult he was either ostracized or lost touch for some reason and they passed away years ago.
Blowtorches are very common on farms as they’re required to repair farm implements and equipment, as most farmers back then were jack of all trades in order to keep the farm operational.
If I were to guess, I’d say Sam worked in the area and there are people who aren’t talking. That’s not totally unusual in rural areas either. Generation after generation, decades later marriages interconnecting families, old secrets can get buried.
JMO