Greg Theakston (1953-2019) was a well-known comics artist and illustrator and here we have an unpublished piece, likely from the 1970s.  I don't know who wrote "found in Ron Patrick's closet" but it likely was David Hartwell himself!    It's a charming image, very appealing, in acrylic or oils on canvas board, 18" x 11.25" and is signed center right in the image. There is minor soiling around the edges and a bumped top right corner... otherwise looks great!