There are a few unexplained phenomena in the universe that physicists do little more than shrug their shoulders at. Any of them could be evidence of other life, and there are proposed theories suggesting as much. We can't prove anything definitively because we're too limited in how far we can go towards explaining the unexplained, but I'd say there's an asterisk on "nothing".

Nah. The distances are too vast. Even if you could touch 1/4 of light speed then that means to get anywhere you take light years and x4 and you start to see the issue.

Then there's the time dilation thing. Suppose you do see some evidence...so u fly towards it. Only in the time it takes u to get there the civ is gone.