Right, and it seemed incomprehensible at the time, just like this glove by the side of the road does. However, from what we now know about the Idaho murders, it seems a likely scenario was that Xana maybe was making noise, maybe approaching the stairs and spooked him, wherein he suddenly needed to take care of her, rather than make sure nothing was left behind. He then encountered yet another human being to deal with (Ethan) and subsequently just vamoosed, thinking he was going to be there all night at this point.
So, I'm thinking that right now leaving a glove by the road might just be a factor of whatever was happening at the time, which was a LOT if he did, indeed, have a kidnapping victim on his hands. Lot's of things to keep track of (seems like several pairs of gloves, other stuff, like whatever was in the backpack, etc.) And, speaking of keeping track of things, it's always looked to me like he had maybe a couple of pairs of trousers on, maybe to protect him from DNA? Anyway, the trousers seem very tight to me and maybe even contribute to his somewhat slow movements.