Excel 2007 : Hidden columns are now gone upon save and re-open

[beckya59]

Hello, I have two spreadsheets that have missing columns (Excel 2007). These are large spreadsheets that I have hidden columns so that I can work more easily and when I have reopened them the hidden columns are now gone completely. I am an experienced user and do not think that I accidentally deleted the colums instead of hiding them. Is this possible, that when saving and reopening the spreadsheet the columns could just disappear? Luckily I had older backup copies so I am able to recover some of the data, but I am concerned that this has happened twice now. Thanks for any advice -