problem---loss of data when using shared workbook in Excel
 

In my work, I need to get feedback from different groups of people. So, what
I do is that I use a shared workbook in Excel and ask all different groups
people to enter their feedback in the Excel shared workbook. This way, all
the feedback can be saved in one master spreadsheet. However, some people
informed me that their feedback is disappered. They saved their data in the
shared workbook, but when I opened it later, there is no data from them.
How can I fix this? Any suggestions?