This, but without the "Find my". Not sure if my cousin would have been able to log into his account from another phone (maybe MFA would be a blocker if he tried), and my hotspot didn't actually provide Internet anyways.

I thought about "relaying" the place's Wi-Fi connection through a chain of phones sharing via bluetooth and Wi-Fi, but luckily we could find the phone without having to try that. The setup would have been something like:

Router <-Wifi-> Phone <-Blutooth-> Phone <-WiFi-> Phone <-....