Mounting doesn´t mean anything... females will mount, especially if there´s not an available gander. I have one goose that is broody-crazy. I have to watch her, because if she has just one egg left unhatched in her nest, she´ll not come out to look after the ones already hatched, but she´ll leave the gander to look after them, which he does but not as well as the goose, and if I take the egg away from her, she´ll find a stone, or a bit of wood, to sit on! She´s a real terror. I have to fence off the area of her nest to make her leave. Once she´s off, she´s a great mum.I ended up letting her run thru it. Funny thing is that the other goose (presumed to be a gander as it has been seen on multiple occasions mounting the other) eventually sat with her for a long time and stayed several days after she gave up.
What caused you to lose the other one? Could it be that it was actually a goose that got egg-bound?