furtive

marked by quiet and caution and secrecy; taking pains to avoid being observed

Stolen; obtained or characterized by stealth; sly; secret; stealthy; as, a furtive look.

Latin 'furtum' - theft

“De Craye saw him cast a furtive eye at his heels to make sure he was not followed, and thought, "Jove! he may be fond of her.”

— George Meredith, Complete Project Gutenberg Works of George Meredith

“Other adjectives discussed by Holmes and Kerouac were "found" and "furtive".”