Thanks for the responses. Unfortunately no previous game. It was corrupt. I did come up with a work around though. Without doing another save until I was sure it would work. The diploma was in an additionally purchased house, so I deleted that house, and replaced it with a previous copy of the house from the library bin. I wasn't sure if it would still have her name on it or how she might react to it. I had her purchase the new house and go there. The diploma still had her name and she was excited to read it. As far as I'm concerned, it worked. So I have it back.
This is the reason I keep the 3 types of copies in the library. You just never know when you might need an independent resource. The house with family, the family, or the house. Thank goodness for small mercies.