The only way to really prevent fibers from falling out is to secure the fiber to the weft with some kind of sealant material like a caulk or to style the fiber with something that basically turns it into a solid chunk. If the fibers can move around, and the possibility exists for them to pull out of their base, they can fall out at some point.
It sounds like you want a flat ribbon of fiber down the front of the jacket that doesn't shift around. You can do that with hairspray and the heat of a hairdryer.
FF9 cosplay? Hit me up!
I now have a Tumblr
. Sometimes I use it.