We don't have a second home (dreams!) but we airbnb'd our house for a month last summer when visiting my sister in the far east.
Rented a storage unit for all out actual stuff and left the place looking very naice and empty and clean - and as we were crawling out the door with the sleeping kids, I put out some ornamental things on the living room Kallax (which is usually full of boxes of toys!) just to make it look more homely.
I should have thought it through more :(
The loss and damage we suffered that month cost thousands - bifold doors broken, Silestone kitchen worktop chipped, and every single ornamental bit I'd left out taken... some of it had real sentimental value. I was so gutted.
We were lucky that we could claim on the (additional, specialist) insurance policy that my clever DH took out, to 'make good' the bifolds and have a reputable company do a passable repair of the Silestone - you can see it if you look though! :( But the things they took were irreplaceable. A pair of hand-carved Finnish wooden cups that my deceased godmother gave us for our wedding... I mean they are cute, but certainly don't have re-sale value, I just put them out to fill an empty shelf! It was a real 'supermarket sweep' type job.
We reported to the police on email and got a reply asking us who had access. It was 7 groups of guests and the cleaning firm. I think it's possible that some of it was the cleaners, honestly - especially as they were doing turnover between each group and didn't report anything. They knew we were out of the country too.
But of course we have no proof so there's nothing to be done.