I saw an interesting theory on reddit suggesting there could have been an accident (drug related or otherwise) at the poker party that resulted in Josh's death. His friends at the party could have feared liability for his death and decided to dispose of his body in the dumpster. If the garbage truck picked up his body from the dumpster it could explain some of the inconsistencies with the scents picked up by the search dogs as the truck could have gone to the abbey after Josh's body was picked up, same for the scent picked up on the bridge. Not trying to spread any false rumors but curious to know if anyone else has considered a similar scenario.
Edit: removed part using someone's name