I may well have told this similar story before ...
... many moons (decades) ago, a year or two into the life of a brand new (large) hospital, the nurse in charge of the Operating Theatres suddenly realised that 'her Theatres' were not numbered logically - it was something like ... 1, 2, 3, 4, 5, 7, 8. Not long before one of the maintenance staff was scheduled "to renumber them sensibly", someone started thinking more laterally. Discussions were had, builders were located and interrogated and, eventually plans were found and studied.
This led to some men with tape measures and heavy tools being summoned. Under a couple of inches or so of plaster, they found a door beyond which was the 'missing' operating theatre, fully tiled (walls and floor), with all services installed (and still functional), even an operating table and light, and all the expected 'furniture'.
One really has 'to wonder' about the person who did the plastering (deliberately or otherwise)
Kind Regards, John