There's really nothing interesting in this crazy theory that someone was wandering around Luz opening shutters.
It may be constructive to solve it first with no occupants present.
Imagine this scenario:
One evening a family on holiday all go out for a meal, and when they get back they find a shutter and window open, traces of someone climbing in the window, and some cameras phones passports and jewellery missing.
The solution is easy: a thief opened shutter and window from outside, climbed in through the window, and stole small items that can be sold easily for drug money.
But that is not what happened. So now try this one
Now imagine this scenario, it is exactly the same but with just one thing added, which changes everything:
One evening a family on holiday all go out for a meal, and when they get back they find a shutter and window open, but no trace of anyone climbing in, and no valuables missing.
Another easy one to solve: a thief opened shutter and window from outside, but at that moment the thief was disturbed by someone and made a quick exit from the area, thats why the thief did not climb in, and didn't steal anything.
Does not that second scenario match well the scene discovered? Entire post obviously is IMO