This also happened to me! I bought my Mocha from a man who let her hatch her ducklings. The day she hatched them, I bought her and all her ducklings. But I kept them separated and sold the ducklings. Once she started laying again I took her eggs and then she disappeared for about 3 weeks. That is when I followed her and found out she made a nest under the brand new coop I built and hadn't allowed any ducks into. a couple weeks later she popped out from under the coop with 5 ducklings!