Do discarded parts (stages, etc) get deleted if they are not part of an active flight if they've be set on an orbit that should take them into aerobraking territory? I've been using a "tug-boat" to chuck some garbage from my space station back to a 45,000m Kerbin orbit assuming they'd crash on the planet and be deleted I then re-dock the tug-boat, but now I'm wondering if that garbage is actually being deleted after observing that non-active flights don't seem to obey they normal laws of Kerbin physics.