If you opened an attachment while using the Internet and went straight into editing the document, you are editing a document that is stored in your Temporary Internet Files location, which is a location deep (and often hidden) inside your Windows profile. Even if you download it, you run the risk of losing the file if you do not back it up to cloud-based storage (e.g. OneDrive). Many times these files are given very long, complicated names, and are lost due to clearing the browser's history and/or cache. The files in Temporary Internet Files are not designed to be intentionally saved, but are instead cached copies of web pages, images, etc. that make browsing the web much faster.
We recommend that prior to editing your attached document that you save the file to Microsoft OneDrive, Google Drive, or another cloud-based storage location, and then open the file for editing.
BE CAREFUL! If you save your attachment to the computer make sure you make a backup of the file to OneDrive or Google Drive, otherwise you will lose the document after you log out of the computer.
