1. How can I check which site template (from site library) did I use on my website?
2. You had a template called ‘one’ as far as I remember. Now, I don’t see it in a site library – has it been removed?
1. There isn’t a way unfortunately. Looking at the link you’ve provided, I’m guessing it was one of the Page Builder Elementor sites: https://www.screencast.com/t/JD2SeXvT8Eoc