There are a few possible reasons why Outlook may have disappeared from your computer. One possibility is that it was uninstalled accidentally. Another possibility is that a software update caused it to be removed. If you are still using the same computer and Outlook was working previously, it is likely that the program was either uninstalled or updated.
If you think that Outlook was uninstalled, you can try reinstalling it from the Microsoft website. If you think that a software update caused it to be removed, you can try restoring your computer to an earlier date.