Not only did I save it multiple times in the process of creating it, but I had emailed previous versions of the document. I downloaded the emailed documents and they also show only one sheet. They had 3 sheets when I sent them.
In which file format did you save your document? Did you use the *.ods format?
I hope you saved it not into CSV format?
I saved it in *.ods. I was able to find a copy of the original version on my backup system that still has the additional sheets. Unfortunately, the data is old and I have to re-enter everything. Still confused as to why the sheets were lost in the subsequent versions.
Please look for properties of the document. Is there really only one sheet under Statistics?
Sheets can be hidden. Then they are not visible at first. But you can show them again.
It is also possible that the Sheet Tabs are not displayed at all.
Properties of the document only show one sheet.