Currently I'm travelling, so only a short text
Briefly:
Could false vacuum be a big filter.
The idea:
highly developed alien (Type 1-3 Civilisations) do research.
They for example put the higgs field in a lower energy level.
The following energie wave is not fast enough to destroy the entire universe (till now [and it may won't ever do if the universe expand fast enough(at least the universe would not suffer heat death)]) but it will move around the speed of light. That would mean that every evidence that this civilisation existed would be destroyed including radio signals space ships and even emitted light that we can pick up with telescopes.
That was typed in a hurry so please excuse my mistakes and the lag of explanation of
the scientific words.
Your,
Isfet