You asked "if you know the Tree Owner, having previously visited their tree, how is it possible, or what is the easiest way, to revisit their Tree?"
There are two places where you can copy and paste urls of an Ancestry Member Tree:
1) Create a source citation for the tree to a fact of a person and copy and paste the url of the desired ancestry tree for that person to the Web Address Box.
2) or use the Web Links tab in the row of tabs in the Person tab, below the facts and above the notes. Give the Web Link a title and paste the url there.
If you want to know the tree owner, it is near the top of the assoicated Ancestry Member Tree page that your url is linked to.