In one week? In a foreign jurisdiction? Knowing how things are done in Mexico it is difficult to imagine forensic techs on their hands and knees with tweezers picking up frags, and even harder to imagine the entire mess being sorted and assembled from multiple devices and then ID'd and traced in time for a summary report.
My best guess is that they recovered unused ones left at the scene.
In the previous answer i was being a smart A but in my day all the parts were made of steel so I imagine a good magnet would gather all the pieces, then start sorting for serial number fragments. Possible to do? Maybe but not probable, IMO.