Hello, the initial source is the photos I took. With a few photos I tried to pull in my POIs possible and enter them in OSM. Then I use my non-google search engine, to expand the information. Most of the times, I find a website of the POI, which you can find in my many edits (I use also info from facebook pages of businesses, but lately I stopped adding them under the website field). After your query, I checked some of my edits, and I see that I added emails most of the times, whereas google has not such info.

Especially for the POI, you mentioned, I remember checking online because I thought I forgot something there, the photo was not clear. And I found a website then entered the info. 