The 'FileRef' attribute as a lookup includes the record ID and everything in the filepath/name after the domain, delimited by ";#"
If I had a file with an ID of 25, located at
Geoff
If I had a file with an ID of 25, located at
"https://www.mydomain.com/sites/sitename/Library Name/File Name.docx",
the "FileRef" field for that file is...25;#sites/sitename/Library Name/File Name.docx
Using my example, your query will work if your argument "actualFileName" is "sites/sitename/Library Name/File Name.docx." I suspect you may not be forming your variable value correctly.Geoff