I'd have to think the better ones ears are at localizing/pinpointing a sound source, the more difficult it becomes for the sound source to "disappear". The lessor the total number of speakers, the easier it is to detect any particular ones location. And of course the recording, the room/environment, the particular type/design of speakers and their placement certainly play a role.
Speakers "Disappearing"
I have read a lot about speakers "disappearing" so that one can't tell from where the sound is emanating. But, what about all the stereo tunes where the recordiing engineer intentionally pans the music to come from one side or the other? Can the speakers be made to "disappear" in that situation? Or, is it just the nature of the particular recording?