My CX300's "grill" detached itself while I was cleaning the ear wax and was lost in the process since it was so small. Probably ended up in my ear as well considering that it was jerked out of my ear with such a force.
I paid good money for my CX300 and like yours, it comes with authentic packaging, L shaped plug, rubbery/matte J shapes wires and so on...
Thought it was genuine at first, but I'm not sure anymore. Those chinese have become way too good, it's like trying to differentiate a rolex with a good copy one.
ADDED: Cracked opened my CX300 and there are like 7 holes in the speakers. 6 "big" holes surrounding one "not-so-big" holes.
Doesn't look anything like the authentic or fake inner workings.
I am so pissed off right now. Next time, I'd make sure I'll get something that is not hugely counterfeited. Like Shure E500... lol