I've been working through all the secret locations for the Finders Keepers achievement. I've successfully received the 'chime' sound for 71 or 72 out of the 73 secret locations.

The final secret location on the balcony near the end of Chapter 4 (A Friend in Need) did not chime on my first run through the mission. I've now replayed the mission from the start and once again, no chime. I've swooped all around the area without success.

Is there a fix for this issue other than maybe starting a new game?