The King lets it be known that he suspects a member of his court of high treason, and that the miscreant in question has been making use of the royal spacehopper.
He also 'lets slip' that the spacehopper has been coated with a special compound that only shows up under ultrafluorescentintraviolet light, the kind of light that only shows up under a special scanner, the kind of which only one exists in the entire kingdom...
The King then summons his whole court together, and displays unto his subjects the special scanner inquestion. He proclaims that each member of the court shall have their hands scanned for traces of the special compound that only shows up under ultrafluorescentintraviolet light. As each member of the court passes their hands under the scanner, the King watches and bides his time. Sooner or later, the miscreant will surface...
The court jester places his hands under the scanner, his hands scrubbed red raw. The King notes this, and wonders if the jester has done his utmost to obliterate any traces of the special compound that only shows up under ultrafluorescentintraviolet light.
Then the king calls his elite guard to his side, and obtains a pistol. And shoots the Grand Vizier in the face. It's always the Grand Vizier. Grand Viziers are evil, it's in the job description...