Hello Oldtimer. Classifieds software is very different from our Forum software. I wish it were as stable as our Forum vBulletin, but PhotoPost ad software is about the only product 'out there' for this type service. It makes tracking or reversing your problem very difficult. Minor input issues or other idiopathic problems spontaneously changes the 'Sold' status on occasion. I checked the administrators log and no human action did this. I apologize.
Can you still see your ad? Send me the web address (URL) if you can. Otherwise I can only suggest placing the ad again. Everybody could benefit from a suggestion -- save a copy of your ad text and 360 x 360 pixel max (60kb or less) photos. That makes redoing the ad easier in the event of a problem like this or a hangup at renewal time.