If you check the article it says it's the 2nd case, the girl's parents notified the Dubai authorities

It was the mother of the girl. She got back to the UK found out about the boy and contacted the Dubai authorities. Apparently the girl was days off her 18th birthday too. It was in the news report when he was originally arrested.

Wrecked a young man’s life for some bullshit reason.

You already know that Mommy phoned it in but after reading several articles I'm going to guess she did it because her family is Muslim. According to another article his family knew about it but didn't care however she was hiding it from her family because they were "quite strict".

I won't discount racist assholes of course but you'd have to be SERIOUSLY over the top to know about this law in Dubai, let alone be willing to make an international phone call to the Dubai police about it. This smacks of religiously motivated behavior.

I think either of those are super plausible. There will be people where they stayed who are happy to snitch, no bugs required. On top of that, the UAE has one of the highest concentration of surveillance cameras in the world. Like 30,000 in Dubai. Throw in some facial recognition cross referenced with the list of folks on vacation or on business in the city and it's real easy to find out who is spending time together, what their ages are, and what their kids will look like.

The second one happens all the time. Happened to me when I turned 18 before my then girlfriend. Her mom threatened me with jail and all kinds of shit even though it was perfectly legal and we were only a couple of months apart. She just didn't like me or the fact that I was dating her daughter. Would have probably been worse if I had been a PoC.

You've left out the good old snitch, my understanding is they're pretty darn strict with anything that involves women over there, so maybe someone from the hotel saw something and reported it.