A319 First Officer discovers a package of unused lock washers attached to the #4 wheel; apparently left there by maintenance who had replaced the wheel at the previous layover station.

Narrative

Upon arrival at the aircraft for an early morning departure I noticed the logbook was not on board. The First Officer did the preflight outside; finding nothing unusual; while I preflighted the cockpit. Approximately 30 minutes prior to departure time; I checked with maintenance about the logbook. They were finished with it; and I retrieved it for review. Maintenance had just completed a service 3 check; 45 minutes prior to our departure time. I noticed a deferred APU had been cleared; and the #3 and #4 tires were worn to limits so they had replaced both wheel assemblies. Satisfied with the logbook; we departed. During the exterior preflight for the return flight; the First Officer noticed an item attached to the right outboard wheel. It was a small plastic bag of lock washers safety wired to one of several holes in the wheel with a Consumable Inspection Record paper inside. We were told that they are for use when changing the wheel assembly where brake fans are involved (no brake fans on this aircraft). While maintenance should have removed the bag prior to releasing the aircraft to service; the First Officer failed to notice it on his preflight. I believe both the early hour and darkness contributed to the oversight. Also; we were unaware of any specific maintenance done at the time of the preflight since we did not possess the logbook at that time. In the future AFTER reviewing the logbook; one of us will re-inspect areas of the aircraft where overnight maintenance was performed.