No time to go look it up, but my guess is it's that painting of the lady on the swing, losing her shoe. But now I can't remember the artist! Boucher? Fragonard? One of those Rococo blokes.
It's Happy Accidents of the Swing - Brian has it by mentioning Fragonard (one of those Rococo blokes).
The only reason I knew this one immediately is because I once used this painting in a challenge on another forum to "modernize" the painting.
I knew I'd never match those trees or the hazy ephemeral feel, so I attempted to make it family friendly, instead.
I never finished it, though - I scratched out my flying shoe because I thought I placed it too close to the trees, and then never went back to add it and tidy up the rest of the piece. I liked my idea, but hated my execution - story of my life with oil pastels.
Here's the entire painting:
Here's my abandoned/unfinished attempt at a challenge to "modernize" it:
Oh well. Maybe I'll hunt for it sometime and finish it.