I don't believe she knew who had it. She dropped it when she attacked Kanon and ran away without it.
I do think she figured out that Haqua, Keima, and Elsee are her enemies though. Whether she knew Kanon was there and came to finish her off, they either didn't say or I don't remember. I believe she was attempting recon.
Keima purposefully didn't show the horns on the locator when he pulled it out of the bag. He knew that whoever had been using it would go for it to verify if it was their lost goddess-radar. A rather clever trick that also allowed him to clear Nora. Fiore was suspect from the start due to his game-related reasoning.