Gig Taggr is not finding photos from an event, but I've definitely got some on Flickr
Gig Taggr searches Flickr based on your photos' 'Date Taken' info. Check the 'Additional Information' section on your Flickr photo page for 'Taken on ...'. This information is recorded by your digital camera, so if you dont have the time and date set correctly on it, your photos won't get datestamped.
Flickr allows you to modify this info once your photos are uploaded, so head to the Organizr, modify the dates, then come back and try GigTaggr again.