Hey Brad - Welcome aboard!
Your images didn't show up in your post, but I'm not sure why - you included them properly.
OK, a few things come to mind:
Downshifting (or any driving) won't cause the cap to pop off. No worries, not important.
If something came off the clutch slave or master cylinder and fluid came out, then you're likely needing a new component. The bleeder isn't easily removed - in other words, there's no real way to introduce air into the system unless something breaks. Unfortunately, they're plastic, so it wouldn't surprise me if that was the case.
I'm almost positive your clutch and brake do NOT share a common reservoir.
Here's some info on bleeding your clutch that may be helpful:
http://www.nicoclub.com/service-manual? ... 7/hatch/CL