If you're trying to open a document from a view, using a stored @Text(@DocumentUniqueID), that don't match the documents UNID, you may get "Entry not found in index" when trying to open the document from the web.
It seems the Domino Server "mistakes" a 32byte hexadecimal string to be the UNID of a document, and ignores the values in the first sorted column of the view.
The quick and dirty workaround is to add a character or two before the stored ID (e.g. "u_" + UNID), in the sorted column of the view, and in the links that point to documents in the view.
The best-practice solutions is for fix the application, and remove a stored UNID as a lookup-value. The simplest alternative is @Unique.