When you OPEN a document directly from an email from an email, a TEMPORARY file with that name is created. If you work on it and then save it, you are saving THAT file. There is now a difference between the file that is attached and the file you worked on.

When you are done, the temp file you worked on AND SAVED, is deleted (sometimes, sometimes not).

This is not new. Microsoft has warned against this (and still does) for years and there must be hundreds of threads like this, on forums like this, going back more than 10 years. You can try searching for numerous threads with extensive details on how you may - repeat MAY - be able to get the other file. It is iffy.

Now you know. NEVER open a document directly from email. Always save it to disk first, then open it.

BTW, ditto for working directly (opening and saving) with files on a USB stick. Do not do it.