That's the most common problem with me too roteague. People wandering into shots at inopportune moments.
Last summer I had my old Graphic set up on a rocky beach in Maine, a sort of "secret spot" (which I'll share with anyone who PMs me of course ) that is about a half hour's hike from the trailhead and is inaccessible from either side because of rocky cliffs. We took the kids there to play, surf, and explore when they were young and it was never crowded. This particular day was a typical summer day on the Maine coast - a heavy cloudbank over the ocean brilliantly lit by the setting sun, focused through cloud layers almost like giant celestial barndoors. I had just set up when I noticed a large multi-masted schooner coming toward me. It was under full sail and was a wooden ship gleaming with varnish and brass. The sun lit the sails perfectly and the skipper was headed inshore and obviously about to make a full crosswind turn, emptying and refilling the sails.
Of course, at this exact moment a woman stepped out from the end of the trail, walked into the exact center of the composition I'd set up, spread out a tatami mat and shed her clothes. Too late to move (and unwilling to go ask a 60-year old naked woman to move) I just shot the scene as is. I guess that's why some folks turn to Photoshop eh?
PS: The woman pleasantly but firmly refused to sign the model release that I finally got up the nerve to bring to her.