They didn't have 'the phone'. They only had traffic logs and had to find the app that matched a certain traffic pattern. And they did have 'something like ElasticSearch', it's all in the link, and even in this reply.
It sounds like they did have the phone. Otherwise, Wikipedia is doing some sketchy stuff if they can figure out what apps are on my phone just from my IP address (IMO unlikely)
> We did this by opening the popular apps one-by-one and noting down the time