Very seriously doubt it was a ruse as much as incompetence or a plain old mistake. Test strip A was most likely a true “test strip” that is used to calibrate the machine on a regular basis. These strips are deliberately designed to cause a positive result so that screeners can ensure the machine is functioning properly. After using one of these to calibrate the machine at the beginning of shift, the screener performing the calibration simply forgot to throw it away and your screener picked it up and used it on you.
There may have been an element of incompetence involved.
Perhaps the screener simply was incapable of doing his job in a professional manner. Perhaps ALL the cameras watching these events really did fail at the same time.
Here’s the thing, however: once the screener flat out lied, and stated that he’d not touched another test strip, once his supervisor (whom the screener had TOLD he’d handled another test strip, and who probably saw him handle the test strip) backed him up, once the TSA decided to go forward with this process based on this obviously flawed test ... that eliminates any possibility of innocent mistake. It’s not just that they performed the test wrongly, it’s that they clearly and unequivocally lied about it.