The missing couple had checked out and were therefor presumed to have left the area.

Well, never presume. It makes a pre out of ... wait, this isn't working.

Already, we have important lessons learned.
1. the heli-skiing company spots an SOS, determines that it's not from their clients, calls the resort. They assume the resort will report it.
2. the resort does a check on their guests. They assume that (a) any missing skier will still be checked in to his room, and (b) any missing skier will have parked in above-ground parking. They also assume that the heli-skiing company would have reported it.
3. the resort assumes that one of their employees, who is a SAR volunteer, will notify the volunteer SAR group. That employee, in turn, assumes (naturally, I think) that his employer has notified authorities.
4. when RCMP gets involved, the resort assumes they're talking about a two-days old signal, not a new, different one. Fatal miscommunication: the RCMP fails to initiate a search.

Lots of people making assumptions here. First lesson learned: when in doubt, call it in.