I think you were just lucky Sadie. Leaving young children alone in a hotel room or in a holiday apartment is just asking for trouble imo.
I think it’s more likely that you’d be terribly
unlucky for something bad to happen. Thinking of my own children when they were tiny, apart from when they were young babies or on the few occasions when they were sick in the night, they would sleep right through, never got up, never cried out. We never had a fire, we were never burgled in the night, no sudden sink holes appeared, I never had an occasion to pick them off the floor where they’d fallen out of bed or off a sofa, or pull their fingers out of a plug socket, or rush them to A & E after drinking bleach and just one occasion when I had to retrieve a purple fuzzy felt dinosaur from the mouth of my young son (though that was during the day anyway and he had not been put to bed but was playing in his room).
I’m not saying “it’s fine to leave sleeping kids alone” because bad things like those I have described above could happen, but the likelihood is small. It would still be incredible bad luck if a terrible thing did happen imo, but the way some people go on about it you’d think leaving sleeping children alone for 30 minutes at a time was akin to dropping them off asleep on the hard shoulder of the M1, an almost dead cert that they would have a life changing accident or worse.