The text is undoubtedly lost. One possibility is that you inadvertently brushed the space bar which would have deleted the selection. CTRL+Z would have undone the change, but not once the document has been closed.
You could look in the recovery folder (usually a sub folder of your document folder) and check the dates of any files that are there. If there are any files that are appropriately dated and have sufficient file size, you may be able to open them in Word. Failing that, and if you feel so inclined, you may be able to open them in Open Office, but adding Open Office may create a few problems of its own.
AutoRecovery is designed to aid recovery following a cash (you have not had a crash). It is not a file backup. If you want a true file backup see
http://www.gmayor.com/automatically_backup.htm