I don't think so but you can do the following to find all photos NOT in a collection.
Select ALL the collections.
Select all the photos Menu EDIT/SELECT ALL
Click on "All Photographs"
Do Menu EDIT/INVERT SELECTION.
All the photos now selected are NOT in a collection.
Before trying this selection technique, it's probably a good idea to first choose "All Photographs," and then
Photos > Stacking > Expand all Stacks
Any images in a stack will not be selected, otherwise. When you're through, you can tidy up by once again choosing "All Photographs, and then
Photos > Stacking > Collapse all Stacks
You are definately correct. I forgot about that little gotcha. Also, photos in a publish service are considered to be in a collection as far as Lightroom is concerned (they show a badge in the thumbnail) but they can not be selected at the same time as the other collections. The OP probably doesn't want these in the final selection anyway.
Awesome thank you so much!!