Hi Nicola,

It sounds like your Excel window may have been minimized or hidden. Here are a few steps you can try to get your spreadsheet back:

1. Check if the window is minimized: Look at the taskbar at the bottom of your screen and see if there is an Excel icon. If there is, hover your mouse over it and see if a preview of your spreadsheet pops up. If it does, click on the preview to maximize the window.
   
2. Check if the window is hidden: Sometimes, Excel windows can get hidden behind other windows. To check if this is the case, click on the Excel icon on the taskbar to bring up the preview. Then, right-click on the preview and select "Restore" or "Maximize" to bring the window back into view.
   
3. Use the "Arrange All" featu If you have multiple Excel windows open, it's possible that your spreadsheet got buried under another window. To bring it back into view, go to the View tab in the Excel ribbon and click on "Arrange All". This will show all open Excel windows on your screen at once, and you can click on the one you want to bring it to the front.
   
4. Try closing and reopening Excel: If none of the above steps work, try closing Excel completely and reopening it. Your spreadsheet should still be there when you reopen Excel.

I hope one of these solutions works for you!