Hi Adil,
By default, Notepad is configured to continue the previous session when launched. If there was unsaved content during the last Notepad session, the temporary file is saved in the Notepad app's data folder.
To see if there are any temporary files (unsaved content) created during the last session, please open the following folder:
%LocalAppData%\Packages\Microsoft.WindowsNotepad_8wekyb3d8bbwe\LocalState\TabState
Backup all the files by copying them to a folder on your desktop.
Now, launch Notepad and see if it restores the earlier content.
If Notepad doesn't restore the unsaved content, you should be able to restore the content from the copied .bin files from the TabState folder.
Important: If the option "Start new session and discard unsaved changes" was enabled earlier, the above methods do note help. In that case, there is no way to recover the unsaved data.