I haven't had this particular problem, but I have hosted a guest that was hiking around Europe, and did not have a smart phone, which is a position that I am in myself. I have an old school Nokia mobile, for calling and texting only. I use the app on my tablet, but don't have a sim card for it, so I'm reliant on WiFi. However, I also live in a country that has free WiFi absolutely everywhere, but this isn't the case for most European countries, where you must pay for WiFi. I've even been refused service in Costa Coffee in the UK, where we'd paid for WiFi,but couldn't use the voucher, because they could only be linked to a UK phone number, which I don't have. It was a stupid and frustrating situation, in which Costa was the only place available, and yet I still couldn't get on the net.
I mention this, because it's easy to forget that WiFi isn't always as readily available as you might think. I've also been frustrated about a guest's lack of communication, until a kindly host in the Host Circle reminded me that people that are travelling may not have a charged phone, or be able to work out how to access data services in a foreign language and system, or whatever. I do understand your frustration, but it's not always that simple.
However, it seems like this guest has raised some flags for other purposes, and this could be one more way to push boundaries. I guess you'll have to fall back on your instincts in this case.