You know, it sounds like he wants looking after. Whether you think that is reasonable and it is something you want to do or not is up to you. And there's a very fine line between showing care and attention and looking after someone, and enabling their unsustainable life choices or untreated depression / SAD. And you know better than anyone here where that line is.
But it does sound like he was pouting a bit because he wanted you there and wanted to be included and wanted, perhaps, to think that you'd planned the day around him. Which is totally unreasonable and if he wants something he can communicate it to you like an adult.
But I wonder if he was exhausted and wanted coddling a bit? Was looking after him and coddling him ever a part of your relationship? Did you do too much of that, and you've pulled back during the separation? Could this be his clumsy way of asking you to come closer? It sounds like it really really bothered him that he turned up and you weren't there. And you know - yes, he should have said what he wanted and expected - but if you've always been the distancer perhaps he's dropped the rope too and he's waiting for you to chase him a bit.
