Last January, we were down in a valley at FDR State Park, and had had a miserable 24 hours of constant rain. Forecast was for it to pass in 6 hours but it just hung over us. Rained all night. Everyone's gear was soaked; temps in the 40s. I could not get a good fix with the GPS because of the surrounding ridges, so I set it on a log to sort itself out.
30 minutes later, as we had climbed out of the campsite and almost to the top of the ridge, I remembered it. It was about .25 miles back (via the trail) but I dropped my pack and went straight down (I could almost see the campsite from where I realized I had left it).
There it was on the log, right where I had left it. I came back up via the trail. It only set me back by 15 minutes or so.