Mobile data disabled and not coming back following a short period of WiFi usage?

I went into a coffee placed and used their WiFi for a couple of hours. As I was leaving, I turned WiFi off, and mobile data never returned. It previously worked without issue.

I tried all the "tricks" Metro customer support typically tells you; toggle WiFi on and off, reboot, toggle airplane mode a few times, reboot with airplane mode on, pull battery, pull Sim card, everything - no dice.

I wonder if it's related to the OTA Marshmallow update a couple of days ago.

Any ideas? My device is an LG Stylo G.