At the limits of thoughts, nothing could disturb, locking out the environment, totally redrawn in himself, we can only guess where his thoughts were wondering around ..... think hard thathaa !
Some of my guesses:
did he forgot where he had put the key of this lock .... ?
had he still a hang over :)) or was he tired .... ?
.... he didn't notice any of the noise surrounding him , nor traffic sound could break his contemplation, he was unreachable far far away !