Mate the dog thing is the real tell there, animals don't lie about this stuff and they pick up on frequencies we can't even register. Had my old terrier do the exact same thing back in 2019, just locked onto a spot on the ceiling and wouldn't move for about 40 minutes, turned out something had been moving around the perimeter of the house too. Cornwall is absolutely rotten with weird activity if you ask me, something about the granite or the ley lines running underneath.
What did the footsteps actually sound like, were they heavy or more of a scraping shuffling kind of movement? That distinction matters more than people realise. Big difference between a fox on the tiles and something with genuine weight behind it. Any unusual smells beforehand, that ones always worth asking.