In many cases, we can expect the things we leave behind to look more or less the same. For instance, I forgot my backpack in a lot of weird places when I was in school and it never looked any different when I finally tracked it down.
But of course, not everything works that way and even the things that can normally stand a little isolation change a lot when left alone under the right circumstances. And while this transformation doesn't necessarily take a long time to happen, it's almost guaranteed to get more extreme after enough time passes.
You've likely seen some of the strange changes on this list yourself but I'm not sure what it means if you've seen all of them.