Yes, that most likely why it got left behind . normally if the egg is dead the mother will throw it out the nest.
Thank you so much for all your help! You most likely will not hear from me again as this was a rare problem for us. Thanks again!!
Come back anytime ! You can stay on BYC even if you don’t have a problem, we’d love to have you either way. But i hope you don’t have any more issues in the future.