Anderson Brass Kantleak repair

After watching the Anderson Brass video on how to repair the 4-way valve a few weeks ago, I decided to pull ours apart to see why it is so hard to rotate. So I pull the guts of the valve out and one o-ring is missing! We don't have a leak so I think the o-ring must have fallen out while I was removing the part (what is that part called?), but I can't find an o-ring on the driveway. So I call Anderson Brass, 2 minutes after they close for the day.  So I go online to see their website, but I get a Microsoft server at go.microsoft.com instead. 

Does anyone who has taken the valve apart remember if it normally is missing one o-ring?

Called Anderson Brass and talked to a Customer Service rep. There are several versions of the 4-way valve and on the first version one of the o-rings is missing because that location doesn't have a function. They installed the o-ring in later versions just to make sure the missing o-ring was not causing problems. So I didn't lose an o-ring.