Radial Filter Pin Off Canvas, Not Selectable

In the future, So people don't have to download the image you have attached, please use the Insert Photos icon found in the Tool Bar of the Post and Reply text entry dialog window as pictured below.
Since you Can't Edit your original post to remove the Attached screen shot Please include the screen shot you attached to a new reply to this conversation by clicking the Blue Reply button under your original post and use the Insert Photos icon in the tool bar.
The Insert Photos icon is this one in the Tool Bar.

Thank you.

While it is not so useful to  place the pin outside the frame for the radial brush, it is very useful to do that for the gradient. Start upper right corner, drag out of frame diagonaly on purpose. let go, instant solid mask. full frame

To select that pin, Zoom out, 1:8, perhaps 1:16

Been their, done that.

You may have started placing the adjustment brush near and edge of the frame, did not let mouse button go, dragged out, then let go, boom, pin outside of frame, some of us do that on purpose.

I tried dragging a radial filter off the canvas and couldn't do it. There was always a tiny sliver of the radial filter remaining in view, and if you put the mouse in the area the cursor changes to a radial filter cursor so you can resize and drag. If you can't see it, you might want to try F7 or F8 to get rid of the side panels, that helps.

do not post attachments, most people will not download them. Post your screen captures via the "insert photos" icon.