Nothing official I'm aware of, but you could hand wave it as the explosion was noticed by someone, maybe a flying plane, whatever, and they investigated and found enough debris to assume the passengers didn't survive. It wasn't explicitly stated but then again the producers didn't really know if they were going to get more seasons at the time so it probably wasn't worth calling out.
Miranda is a YouTuber that started on REI's channel before branching out last year. She's enthusiastic and mentions she's more of a traditional backpacker, and has tried ultralight backpacking a few times. Also, a cute camp dog.
Nothing official I'm aware of, but you could hand wave it as the explosion was noticed by someone, maybe a flying plane, whatever, and they investigated and found enough debris to assume the passengers didn't survive. It wasn't explicitly stated but then again the producers didn't really know if they were going to get more seasons at the time so it probably wasn't worth calling out.