We've hosted au pairs for over 6 years and it's always been fine - this week our new au pair of one week has walked out (just literally WhatsApp and then walked out) and it's totally thrown me.
I think we were possibly not focussed enough on making him feel welcome as we were so used to our old au pair who'd been with us for 18 months. Last week seemed to go okay (I cooked dinner a few times, we had dinner together on Friday) but we also had a relative staying over the weekend so didn't invite him to explore London with us over the weekend.
I also found a picture of our bedroom on his InstaStory (only today, after he messaged us - it was from last week) which makes me feel a bit weird and uncomfortable.
He was 19, from France and had spent the summer working in a bar. He seemed nice and I'd explained everything to him. We have a cleaner so he wasn't expected to do any housework.
He arrived last Sunday at 8am and walked out the following Monday (today!) at 930am.
There is a lot of free time and I'm not sure he has any friends - but he was due to sign up for English classes.