I tend to agree with jrbren... however, you can normally tell a pair of snowshoes that were removed, placed as a pair for later retrieval, hopefully just off the side of the trail, from a pair that has fallen off the back of a pack.
That said, perhaps sdw1 had them just off trail, neatly stacked and forgot them.
This reminds me of the first hike this winter season. I had stashed an emergency water at the Caulkins Brook/Blueberry trail junction, in a good and visible blue bag, in an insulated coolie, and then buried it in the snow to act as an extra insulative layer. When I returned at the end of my hike to grab my water, someone had pulled the bag out to inspect it's contents, then left it ON TOP of the snow. Maybe they thought it was garbage? Maybe they were just Curious Georges? Maybe they thought its rightful owner would forget where he left this very obvious stash and thought they were doing me a favor by leaving it out unprotected in the open. Maybe they have no idea that one of the best ways to keep warm water in a liquid form is to bury it under snow for extra insulation. Whatever the case, the age old adage of "put it back like you found it" wasn't practiced here, but luckily I wasn't in desperate need of that water, only to find someone had turned it into a block of ice for me.
I think one must think a bit before either taking or leaving items we find along the trails. If I ran into a pair of shoes, neatly stacked off trail I would leave them. Though I may think twice if I had gone up from Lake Arnold, didn't see anyone on the summit, and was leaving late in the day. Even then, with a neatly stacked pair I would probably leave them. However, if they were lying about helter skelter, I may grab them, or at least put them up high in a tree along side of the trail.
This does present a tough question. One would hate to run into the woods on an emergency call of nature and return and find your snowshoes missing.