After defining a pivot table and saving - My source data disappear

Hi All.
A very strange happened to me. I hope you can help with the following scenario

I have an excel table with data
I step on the table and selected "insert -> table" to set as a table
I then created a Pivot table out of the entire table selection. Pivot table was created in a new worksheet
After the pivot table was created I closed the spreadsheet. Excel asked me if I want to save and I said yes.

The excel file became 1K size and all my row data disappeared.

Never happened to me in the past and I have no idea what to do.

Any idea?

I am running Excel for Office 365

Thanks and happy holiday to you all