I just took a tip from the two-wheels-and-pedals guys and hooked a bicycle water bottle holder to a ram ball. There's a reason they've used the same system for decades. It's easy to use, efficient, and they've been around so long that there are a gazillion different things that fit it.
Those are much better. And I still don't have a clue -- unless it's the smallest frame slider ever.
One thing's clear, though. If it came off your bike, at least one other part did too. That's not the end of something. Since you didn't find anything else, it's either wfooshee's phantom part...
I think any semi-competent mechanic can handle a valve check on this bike. It's not that tough. If it's a local, small shop guy that you trust, use him (unless you have warranty issues).
I'll +1 that. Just got a reconditioned 550 to replace my old one and came back to these instructions to get it loaded again. This is a great reference.
Oh, go ahead and do the smartass thing on the assumption I'd have missed it anyway.
I actually won't know until tonight sometime if I can go Saturday or Sunday, but odds are I'll meet you at the Starbucks.