I never considered the smartphone thing. Very strange that Piranesi forgot it. I suppose the house works in mysterious ways!

I'm glad you interpreted Piranesi as gay, because I did too. (The part where he runs sobbing into the arms of the faun springs to mind.) It was only once I'd finished the book and read other people's comments that I realised that Piranesi wasn't actually confirmed as gay in the text. It's a strange one. If Piranesi was intended to be gay, why not spell it out, like it's done with the other characters? It would have been the easiest thing to have had a boyfriend waiting for Matthew along with sisters and parents.