The origin of this is when huge queues suddenly appeared out of nowhere. Reynolds went into a Tynwald meeting and said she had no idea what the problem was, but that she wanted £330,000 to fix the problem. The politicians replied "If you have no idea what the problem is, you had better have £670,000 - just in case".
The scanners were part of the solution. The scanners were on display for a short time, but were not used because of software problems.
At the location of the single scanner (which is redundant, because there must always be someone attending the scanner and that person could manage with the same hand-held scanners that are used elsewhere in the airport) you then turn left to the baggage scanners. On your right is an open area that Reynolds designed to handle the huge queues. There are a couple of scanners there, but are never used. As for the others, an FoI request might reveal their current resting place.