I hope someone hands it in and if they do I also hope the damage from the road impact and tumble isn't too bad.
Similar thing happened to me in Sarina, QLD. I didn't secure the pannier frame latch properly and the pannier departed over a rough section of road. Every surface of the pannier had serious road rash. At the time I couldn't find a used pannier so I had to make my first insurance claim to replace it.
I think all the replacement parts cost about $1600 and the lock internals, pannier case handle were salvaged and reused. Excess was $400 on top.....so just preparing you for the worst case scenario!