SAN Three members of the Quicksilver Messenger Service were busted for possession of dope here recently. It all started at the airport when the anti-skyjacking device flashed as George Benney walked past it. His first reaction was to split, but the Feds were on him too f ast. Grass was f ound on guitarist David Freiber.g, and on Benney, who was alsü f ound with a small quantity of bullets (that's what flashed the skyjack checker). José Reyes was accosted for possession of a few pills, variety unspecified. Lails were set at $1250 each. All are free now, and no trial date was set.