Want to hide product from main site but want people to get able to purchase if given URL

I am working with another business and have set up an experience for just their customers. How do I set this up? When I click hide- the URL doesn't work. 

I've done this with a few products in my store. What I did was create a folder (for organization purposes) that's not linked. Then inside that folder, I created a store to contain products I don't want to show in my main site.

Thanks- how does one create a folder? 

Go to Pages, click on the + on the right of Not Linked. You'll see Folder as one of the options.