I was really hoping that Orion had a way to reset a pinned tab to the original URL, and I was only able to find out you can do it with Cmd-click by searching orionfeedback.org (I was going to file a feature request).
We should really make this more discoverable so more people can know that it exists. I suggest adding a "Back to Pinned URL" menu item on the pinned-tab right-click menu.
Arc shows Back To Pinned URL when you hover over the favicon and you can click it:

Orion is different because all you have is the favicon, so maybe a right-click menu item would work better for Orion.