Dell Shannon 
Felony at Random [EPUB ebook] 

A bunch of kids from a Catholic School on a school trip to the Museum of National History seems like a safe day out. But when the nuns counted heads outside the building, young Joyce Mc Cauley was missing. The Feds, believing it to be a snatch, are waiting for the ransom note to turn up.But Lieutenant Luis Mendoza of the LAPD has other suspicions. He has been working with violence and death longer than he cares to remember and has seen it all. Mendoza is certain some nut has kidnapped Joyce, and sets about tracing the girl in his suave, tough and matchless fashion.’A Luis Mendoza mystery means superlative suspense’ Los Angeles Times