"not arrested" ? That's a squibble of words. Innocent people were held at point of gun - apparently through lazy administrative staff - welcome to the land of freedom!
To be detained is not at all the same as to be arrested. The Kings were not arrested, and it's hardly an issue of semantics. The Kings were lawfully detained, were never in any danger, and were treated well.
The issue had nothing to do with laziness. The FAA reissued a registration that had become stale. Law enforcement was not aware of this change, and a mechanism did not exist to communicate the issue...any more than changing one's address at the post office will automatically change it with the driver's bureau.
The scenario worked out very well, in fact, given that a report of a potentially stolen airplane was acted upon quickly and decisively.
Cessna's are popular theft items for use in mexican drug operations. For the police to react quickly and professionally as they did speaks well for the police. There was no disgrace to be found in the way this matter was handled.
That the Kings received an apology none the less was good grace on the part of the police, but hardly a necessity, as the police did no wrong.