Wiktionary
sneak thief
n. a thief who steals without being noticed and without using violence
WordNet
Usage examples of "sneak thief".
And if rumors of a clever sneak thief sent the Watch around on heightened alert, he could stop going for the trinkets and confine himself to listening at chimneys, which sent up no smoke in this lovely weather, but did provide wonderful listening posts.
Kreacher told the sneak thief to stop, but Mundungus Fletcher laughed and r-ran ….
The sneak thief responsible would be far out of sight now, if he had any sense.
As everybody knows, there was a barnyard mimic as well as a sneak thief among the heroes in the Lord of Mengchang's entourage, and Jing Ke used to get drunk with a dogmeat butcher in the marketplace of Yan.