Exactly. Maybe there is no means of traveling beyond the speed of light, so no aliens get very far. Billions of years later the voyager gets pulled into another solar system where there are aliens (that maybe have colonized their local system but not much else) happen to notice it. Unlikely? Yes. But again, this probe will be drifting out there for a looooooong time. Like a message in a bottle. Maybe it will break completely, maybe it will get pulled into a planet in Alpha Centuri.
Or, on the other hand, these aliens may be so intelligent that they look at us like ants. We cannot really perceive their presence the same way an ant cannot perceive us. They may notice us but not even care to bother. They may even build an intergalactic highway right through out planet Hitchhiker's Guide to the Galaxy style, just as we plow asphalt roads through dirt and ant colonies. So the Voyager probe may be like ant or termite crawling into somebody's house; the owner of the house then finds the source of the infestation into his/her house and removes it. IE the voyager may be the beginning of our destruction if aliens think we are simply an infestation.
