Ghosted by a company

So I think I've been ghosted.

Had final round interview for a job last Tuesday the 4th. It was a 3 hour design challenge (3 hours I know wtf). I was told at the end of the interview I would hear back early this week.

Monday heard nothing, Tuesday heard nothing. So I followed up yesterday evening with an email to the person I was dealing with asking for an update. And guess what no reply.

I know at this point that I don't have the job but I don't want them to get away with just not having the decency of letting me know. Especially after going through 3 rounds and taking fucking 3 hours of my time to do a design challenge.

What should I do?

My partner thinks I should give it another few days in case they do eventually respond.