All actual border checkpoints were guarded by staff of the "Pass- und Kontrolleinheiten (PKE)" belonging to Stasi (just wearing border guard uniforms). Whether Schönefeld airport or Checkpoint Charlie. So leaving East Germany one way or the other they would know in any case it's you who is leaving. There was no quiet way out. Maybe the quietest was via Czechoslovakia. As a pedestrian you could even walk over the border at remote places like at Erzgebirge mountainside.