Robert Sides wrote: …screenshot has been taken, but can't locate it in PHOTOS.
I seems like it would be among the most recent pictures, wouldn't it? The newest pictures are right in the middle of the screen when you open Photos, so they should be easy to find.

This all seems pretty simple to me. I mean, the newest things are right in the middle! You might want to consider using a different source for information.
Of course, by "newest," it could be most recently added or most recently taken, so you would need to sort accordingly. You sort in the Library view, a short scoot up from the Photos view:

Of course, you'd want to be sure that you haven't excluded screenshots from the view by checking the filter

Maybe choosing all items.
Or you could go to the Media Types section down by Utilites and just choose "Screenshots."

Which part gives you the most trouble?