"Oops. We were wrong. No giant planet. Sorry."
I like your comment.... Maybe by then there will also be a new theory on global warming, somking and lung cancer, and whether red meat is good for you.
It would be impossible to prove, since our lost giant is probably light years away by now. However, if this sort of thing is common, we might be able to detect someone else’s wandering giant. The empty reaches of space might not be so empty