This is the 3357th most frequent Swedish word.
anträffades
"Anträffades" means "was found" or "was located" in English.
Here, 'anträffades' is used in the passive voice to describe the subject (individual) being found by someone (police), indicating an action performed upon the subject.
Individen anträffades på platsen av polisen.
The individual was found at the location by the police.
In this sentence, 'anträffades' again is used in a passive structure to denote the act of discovery of an item (key) at a specific location (home).
Nyckeln till kassaskåpet anträffades i hemmet.
The key to the safe was found at home.
Here, 'anträffades' communicates the occurrence of locating someone (dog's owner) at a subsequent time (later the same day).