Marking your pack location with GPS is an option, and probably frequently done. However, my personal experience is that even dedicated, modern GPS units will not always get you close enough to find something as small as a pack.
Last year my teenage son and I went on a cross-country bushwhack to chase native trout. No trails. We marked the location of my 4-man tipi with my Garmin and then hiked to a lake. After catching some lunkers, we walked back to camp in the dark, during a thunderstorm; the GPS refused to provide accurate mapping. We were pretty wet by the time we found camp, no thanks to the GPS. I don't pretend to understand what makes a GPS work and what causes them to degrade in function, but they are not fail proof for sure. I would actually feel better doing a resection with map and compass and leaving my pack at that precise location.
Best solution: Take pack with you.