A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
My initial feeling on this is that when the drop-down lists were created there were only 12 columns of data, with the 13th added at a later date.
The drop-down lists are probably the Filter drop-downs.
Try this:
Click into your data
Select the Data Ribbon / Sort & Filter Group / Filter
This will toggle the Filters off
Then
Select all 13 columns (Just in case you have blank lines lurking in your data)
Click the same filter button again.
You should have all 13 columns with filter drop-downs now and they will always sort all the data.
May I also suggest that a list of data can be formatted as a table.
Home Ribbon / Styles Group / Format as Table.
This very effective at keeping data together.