Based on what the MySpace "John Titor" shared with my online friend at the time SnowFireWatches, your last sentence is true.I agree with Einstein, since someone else knows the song there is no way to verify the real John Titor.
...presuming that is the true intent of 'the secret song', as well as the assumption that there isn't another means of doing so.
For all we know, there may or may not even be a secret song, or it could be a hundred of them, or it could be bait for something, ..or anything else for that matter.
Oddly your preceding sentence is causing me to wonder what other intentions there may have been in the idea of 'the secret song'. Perhaps it isn't even worth the extra thought.