Saving an excel file and then discovering it has not saved the latest version

I am using excel 2010 on windows 8 and as a bookkeeper my problem is really major to me!
I load a file which has been sent to me via e-mail and save it with an upgraded name, I then do a large amount of data input and save the file again, I do this regularly and even test load it at times to check it has saved, finally I save and close the file and then on reloading I discover the version I have is the first one I saved! all the work I have done on it has disappeared!
I also sometimes find random .tmp files with non-sensical names in the folder to which I have saved, but I do not have the rights to open these .tmp files.
Can anybody out there throw any light on this - - -Please!!!

1) Whenever you work on files received on mails,
a) ensure you save it to a local drive before working on it
b) ensure you work from the file saved locally and not on the file opened from mail
These simple steps will avoid losing changes done to a file. Else you may need to understand a lot on how the mail client and operating system handles attachments and changes attempted on attachments. I have seen myself and many others lost such files and could not find an assured solution for different environments while I was lucky in a few environments to get back the file.
2) .tmp files are generally created by the Excel application (and many other applications) when you work with a file. Only the application can use it and users do not have access for the same (rightly so).

Thanks, but I think I am working on the locally saved version, I will however double check that in future.