If you can see it when it's just setting out, you know where it's come from. You can dump it in interstellar space and let it float aimless for a while to disguise it better, but then we're back to the big timescales problem.
The acceleration we saw was pretty small, and only detectable at (relatively) close range. Maybe this was an acceptable risk for them, or maybe the local detectability is by design.Furthermore, what even gave us the idea that Oumuamua might be artificial? First, it has an unusual shape. Second, there was the unexplained acceleration as it left the solar system. If your goal was to be stealthy, you'd look like a rock and not accelerate until you're well into intersteller space.
I never said it was. I don't think EyeKhan is saying that either. We're both just saying you can't rule it out yet.It's more a case of "Nothing about this points to aliens having done it". "It wasn't aliens" is the default position here.