Living in the past would explain most of the things rather perfectly. None of the E-D crew would see our protagonists because they would only "appear on the scene" after the crew had "left". However, the protagonists would sense the light, sound and smell left behind by the crew that had just "left" - they just couldn't create any sort of a feedback, because there was nobody there any more.
That wouldn't stop them from making use of the light, sound, smell and air molecules "left behind", though. While chemical interaction with those molecules would be difficult due to the rapidly decaying chance of feedback, there might be enough of it left to sustain life processes. Not enough to sustain the longterm solidity of walls, but enough to sustain the brief electron transfers necessary for oxidation. It might be like breathing thin mountain air, but it could still be breathing.