Tarzack
Yes, but maybe not, the top of the bellows is more 'exposed' in that it is not protected by the baseplate at all, the bottom of the bellows is shielded by the baseplate, and not exposed to direct sunlight in a 6x6 folder where the camera is used horizontally.
If the day was cloudy or the sun was shielded by your body and there was a top of bellows hole then the non desired image is a pinhole photo of the sky, it might be restricted in area by the pleats of the bellows, as your sample seems to be.
Fidget's (Dave's) diagnostics may help you to localise or dark room and light may be used. If you do the tests (a bask in sun with lens cap on for shutter release) on a tripod then the image may be more easy recognised
If it was lens flare I would have expected it to be more general (i.e.extended), but I'd always use the camera with a deep lens hood anyway, independent of faults like this. My FSU lenses give more extensive flare, when stress tested, even with the deep hoods I use. A large camera shop normally has a cardboard box full of old lens hoods, sometimes cheap.
You can do a flare test in a darkened room, it is easy for a lens with foggy interior optics to flare.
If it is a hood pinhole you may find several pinholes if you look carefully, if there is one there probably is several. Greyhound or FrankS says to leave the bellows for 48 hours after spotting the bellows holes with black fabric paint, I'd err on side of caution.
Noel