HELP!!! timing belt replacement parts

Hey all,
So I decided to finally replace the OEM timing belt on my 99 VX since it hit 90,000 miles last month. I followed Bart's guide to a the letter - i even used the sandwich baggies and cardboard box. Everything went smooth as silk until i discovered this (see photo) big washer at the bottom of the box when I was finished. Any one have any ideas where it came from? I checked all the old parts and didn't find any place for a washer. Normally I don't worry about leftover parts when I work on my cars, but since the timing belt replacement is kind of a crucial job… i didn't want to screw this up
Ben

http://www.vehicross.info/gallery/sh...hp?photo=25837

http://www.vehicross.info/gallery/sh...hp?photo=25837

Hi, I did some checking on possibility, and found this schematic of the engine. More specifically, item #13...gear washer: http://isuzupartscenter.com/parts/20...iagram=4628155

Just a thought.

Looks like the washer/spacer that goes behind the tensioner to me...you sure that box was empty when you started...:)