Flushed a unfertilized egg...should their be an embryo with it?

Did your vet give the mare lutalyse to try to breed again? If not, I would think that she needs to be checked again by regular ultrasound to make sure that she’s not pregnant so that there are no surprises later!

Sometimes the embryo is hiding, maybe she just didn’t conceive, but always good to double-check and it doesn’t require flushing again.

Best of luck to OP!