Summer Event: I can't find Doubloons from incidents!Even though you can receive Doubloons from Incidents around your city, this doesn't mean that you will get them with every collected Incident. The Doubloons are considered to be rare rewards and therefore hard to get.
Per day between 10 and 15 Incidents can spawn in your city and will stay there for 24 hours. Afterwards they expire and disappear, and are replaced with new incidents over time.
So, keep your eyes open and search your city regularly for Incidents to be in with a shot to find more Doubloons!