This may be old stuff to many of you, but since this is my first touring bike and I haven't seen this mentioned before, I thought I'd lay it out there FWIW...
Every time I take my saddlebags off the fasteners tend to fall out and down into the saddlebag. If I'm lucky, the washer stays on the fastener and doesn't fall down between the liner and the saddlebag. I put a #5 o-ring (3/8"x1/4"x1/16") on the out board side of each fastener and that seems to keep them from falling out. It doesn't have to be a #5, I just used that because I had a supply of them - it's the same o-ring for the primary drain plug on my softail.
I did the same thing when I got my '08 SERK home from the dealership. The first time I took off the bags, the pin and washers just dropped into the full of
stuff bags. I'm not sure what size o-ring I used, but I put mine first on the pin just to keep the washer with the pin and that was a big help, but then one time I tried it on the outside and it seems to be a bit better. At least you don't drop the pin and washer anymore.
I agree, this is NOT a great design for a company like this to come up with. They could have made a provision in the pin to have a snap ring installed after the pin was inserted into the rubber grommet.
For right now it seems you've solved your problem and I'm not complaining anymore about my pins falling out.
A groove and an "E" clip would be all it needs to be a "fix" from the MOCO.