Trying to think how I could avoid this in future. We usually leave a note saying "To be collected later" with the date. We don't specify the time as this MIGHT encourage theft if people knew they had an hour or so to get away with it, but I don't think that folk go into the hills to steal things, so omitting the time is unnecessary really. Nor do I think that people go into the hills on a busy summer's day to commit suicide. Maybe on a cold wet day....see
thishttp://www.bbc.co.uk/news/uk-england-manchester-38757699, but even that wasn't definite.
What had those folk experienced in the past to make them like that? Had they found a rucksack where something bad had happened to the owner? In that case, they maybe should have told you.
I met a couple once whose teenage sons had begged them to be allowed to repeat a Lake District round. At 15 and 16 they felt old enough. Parents said yes, and just to be sure, followed them a day later. Eldest son fell to his death. Youngest son became a paramedic as he wanted to do all he could to stop things like that happening to other people. I suppose an experience like that could have made them like they were. But as others have said, they were probably just officious so-and-sos.