The recent document list doesn't contain files, it's just a list of filenames.
It's easy to get rid of the file by deleting everything in that C:\users\<yourname>\AppData\Local\Temp\ folder.
And why care about a file that no longer exists showing up in a list? It will fall out eventually after you opened 10 other files.
When I downloaded today, from CNET, Free AVG 2013, very mysteriously a file C:\users\AppData\Local\Temp\avg-83b6....(etc.) got inserted into "Recent Documents" list in my LibreOffice 3.5!! I cannot at all locate that file in my computer so that I can then get rid of it from my computer and especially from my "Recent Documents" list in LibreOffice 3.5.
Thanks in advance for the help.