It is impossible to see the actual egg or oocyte by ultrasound. They can only see the follicle which potentially contains an egg. Sometimes they can tell if you have ovulated if the follie has rough edges and shows some fluid around it but it is pretty much a guess and the best way to tell is by a progesterone test as IM43 said. I would just have them run an hcg pregnancy test before they do any mapping of your uterus just to be sure.
I know an egg, once released from the ovary dessintegrates within 24 hours (I'm hearing a lot that it is only viable for 6 to 12 hours), but an oocyte of course is an egg that is maturing, but has not released from the ovary. Every month your ovaries try to mature many eggs and the first one (or sometimes two) to mature, gets released. Maybe you did ovulate when you thought and the oocyte that he saw was one that was trying to mature but didn't get released. I don't know how quickly the other oocytes that are trying to mature, dissappear after a mature egg is released.
You should ask your doctor if he saw a corpus luteum on your ovary, from an egg that had been released. I don't know if you can email or call them. They can also tell if you actually ovulated by doing a blood progesterone test. If you did ovulate and DTD at the right time, I wouldn't let them put anything into your uterus until you know for sure that a fertilized egg has not implanted.
Good luck to you and remember.... dr's always tend to not tell you anything more than they have to (I think it makes them feel like they are really smart or something). Always make sure you ask questions, ask questions, ask questions and don't stop asking until you understand as much as they do!!!