I'm guessing the answer is obviously yes that this type of x-ray would easily be able to discover / distinguish something the size of what's been described? (1mm x 2mm from what I've seen thus far?)
The x-ray picture would contain information sufficient to detect that thing, but it's quite plausible that the process/procedure of analyzing that x-ray would not find it. If they're looking for extra hardware, they're going to detect it, but if they're looking for bad solder joints, they're going to detect bad solder joints but not extra harware.
