The galaxy is huge but even if a civilization could "only" travel at 50% the speed of light ever (and also if a desire to expand is a reasonable thing these civilizations would have) the galaxy would've been colonized within 100K years or so. So if any time between anatomical humans and now there were spacefaring civilizations in the galaxy, we should see evidence for it pretty much anywhere we point our telescopes.
The galaxy is huge but even if a civilization could "only" travel at 50% the speed of light ever (and also if a desire to expand is a reasonable thing these civilizations would have) the galaxy would've been colonized within 100K years or so. So if any time between anatomical humans and now there were spacefaring civilizations in the galaxy, we should see evidence for it pretty much anywhere we point our telescopes.