Swingarm cap
Hello Terry,
I went riding with Rocky and a coworker one day and we went down some of Indiana's "finest" roads - "finest" = horrible, pothole covered, bumpy, rough, etc. After the ride, Rocky informed me he had lost one of his caps and a few other things too I think. I think they have a tendency to slowly work their way off and should be checked occasionally - or you can put just a dab of silicone on the inside of them when you put them on to help hold them in place.
As for the oil - are you sure it was engine oil and not gear oil? Either way, it looks like you have a bad seal somewhere, at one end of the driveshaft or the other - or both, depending on what kind of oil it was. I would be careful with that, make sure you check your fluid levels, if you have a leak back there, it could get on your rear tire while riding. This could get real ugly and dangerous while riding down the road. Even if it is not leaking out onto the ground, if it's engine oil, then your swingarm could be holding a large portion of your engine oil meaning your engine is not getting it's proper amount of oil for lubrication - the same goes for the rear drive unit - all or some of the fluid could be in the swingarm, and not where it's supposed to be doing it's job - lubricating gears. Gears and engine components without good lubrication can get ruined real fast that way. Hope that helps a little, later.