Citrus County Sheriff's Office said the anonymous woman had used a specialist scent preservation kit.
It can hold a person's scent for up to seven years.
In a Facebook post police said she stored the scent two-and-a-half years ago, and a picture of the jar showed it was dated January 2015.
Scent preservation kits involve rubbing a pad on a person's underarm, then sealing it in a sterile jar so police dogs have a reliable scent to smell before looking for a missing person.
