I use a white T-shirt type cloth to bag dry hops and have never had an issue.
Of course, I have never disconnected my keg and left it charged with Co2 either. I think that was your trouble, not the hops.
Minor chunks of hops will flow through as long as the connectors are not disturbed.
Keg #1: Brown Bomber Bourbon/Oak Vanilla Porter
Keg #2: Lawnmower APA just kicked :(
Keg #3 The Bollocks ESB
Bottled: Mjolnir Mead, Lazy Daze Hefe.