He doesn't have mobile internet connection, so he asks his host to connect to his host's wi-fi.
His host, that we assume for the sake of our inquiry wants to scam his guest, connects him to a fake internet in which the real BTC blockchain was forked in order to fake a transaction that in really will never happen.
I'm not sure how this would work. Is he going to connect the guest to an internet network that he is able to manipulate data from it? I mean, this could be possible, similar to how countries block certain sites, I am sure smart hackers are going to be able to also manipulate things on someone's phone when they try and access the internet (eg, making things show up, after they use the internet).
So once the first guy will go back home he'll see that his payment has disappeared.
Is this situation technically possible?
You could be able to another address show up in place of an actual address possibly, but this hacker would need to be incredibly skilled.