Answer:
It's fascinating that you believe you've discovered a portrait of Lady Jane Grey painted by Jean-Urbain Guérin. Sometimes, artworks can be overlooked or not widely known despite their significance. It could be worth reaching out to art historians or experts in the field to get their insights on the authenticity and significance of your discovery. They may be able to shed some light on why this particular painting isn't well-documented or known in the art world.
