the idea that the perp revisited the woods to intentionally bury the bag for a dog to find is so far-fetched compared to the idea that the bag was dropped and not found during the initial searches. it's also obvious from the picture that the bag has been in the weather for a while. also, since no one knows where it was found no one knows whether it was buried or not.
as to why she would go into the woods clutching her stuff - because she had a test that morning and in the chaos of whatever happened to her she wasn't able to comprehend what was going on, the same thing any of us would do in that situation. she drops her stuff and she's conceding defeat - that she won't make the test, that this is happening, that she's not getting out of this situation. so she walks with this guy into the woods, hoping that she can get out of the situation. at some point during the walk he probably grabs her stuff and tosses it.
my two cents: there is no reason to believe a complicated solution when a simple solution is just as viable.
as to why she would go into the woods clutching her stuff - because she had a test that morning and in the chaos of whatever happened to her she wasn't able to comprehend what was going on, the same thing any of us would do in that situation. she drops her stuff and she's conceding defeat - that she won't make the test, that this is happening, that she's not getting out of this situation. so she walks with this guy into the woods, hoping that she can get out of the situation. at some point during the walk he probably grabs her stuff and tosses it.
my two cents: there is no reason to believe a complicated solution when a simple solution is just as viable.