65 million years is an incredibly long time. I don't think any of you are grasping the scale of time here. What would rebar-reinforced concrete look like after deep burial and metamorphosis at high temperature and pressure for that long? Assuming it would be recognizable and easily stumbled upon by archeologists or paleontologists is naive.
I agree with this. (as I posted earlier)
I also like the idea someone else posted.
We know the Voth do NOT under ANY circumstance want to acknowledge that they were a race that fled a planet, didn't have a home, etc...
ODALA: When I open my eyes to this theory, what I see appalls me. I see my race fleeing your wretched planet, a group of pathetic refugees crawling and scratching their way across the galaxy, stumbling into this domain. I see a race with no birthright, no legacy. That is unacceptable!
So to me it's very plausable they returned to Earth and removed any and all physical evidence.