Can't they just track the ships backwards in time to see wherever they left from? Or find the last time they used their transponders and see what they were flagged as?
I also don't really understand the practice of calling it a "mystery". Yes, after Biden threatened to unilaterally end the pipeline, and Blinken reiterated the threat, "someone" blew up the pipeline. But wait! Even more mysteriously the US (and allies) is the only party with a clear benefit from blowing up the pipeline. Yes, I wonder who could've done such a thing...
I also don't really understand the practice of calling it a "mystery". Yes, after Biden threatened to unilaterally end the pipeline, and Blinken reiterated the threat, "someone" blew up the pipeline. But wait! Even more mysteriously the US (and allies) is the only party with a clear benefit from blowing up the pipeline. Yes, I wonder who could've done such a thing...