The Body at Blackwell Lake by A.M. Caplan

Cora’s strange ability to locate other lost things brings her to the site of a murdered corpse. After the police find no clues to the culprit, Cora allows the victim’s fiancé to persuade her to help him dig up evidence. When she discovers the handsome man is not what he seems, Cora fears the only thing her talent will lead her to is her own grave.