According to this wiki article http://www-10.lotus.com/ldd/dominowiki.nsf/dx/notes-urls since 8.5 notes:// urls can be used to open documents by key.
Does it work for anyone?
I always get “The document specified by the link cannot be located within the linked-to database.”
Martin
Subject: if formatted properly
I was able to get it to work if I used the replica ID and View ID. Specifying that info as names I get the same error as you.
So Notes://acme/register.nsf/Registered+Users/Jay+Street?OpenDocumentByKey does not work.
However Notes://acme/86256EDF005310E2/A4D87D90E1B19842852564FF006DED4E/Jay+Street?OpenDocumentByKey did work for me. (I am using Notes 9.0.4 now though)
I also found a couple more documents on the subject that have probably been posted since your original question.
http://www-01.ibm.com/support/docview.wss?uid=swg1LO61771
http://www.bizzybee.be/2014/03/06/a-simple-workaround-for-opendocumentbykey/