Again, raw LIGO data is sheer noise. They have to interrogate the dataset with their hypothesized candidate signal signature, natural or otherwise, and see if it ‘responds’ with a hit. In the case of black hole mergers, they had an idea - a candidate model - of what to look for. In the case of a warp drive, could they even guess a signature to interrogate the dataset with?

And to the extent that the -1701 patrolling Mars-Venus might manage to ‘stick out like a sore thumb’, what about the relative blip of a Sh'Raan class embarking on some fresh surveying out of 40 Eridani A?