-snip-
-snip-Was it because of wallet version, he was in a wrong chain? If that was the case, I think in the updated wallet, the transaction would not be visible.
I got all the above point but still that does not fit the answer.
So it looks like the second scenario in my post.
Since he's using the old client, it might have created a non-standard transaction and that Tx was rejected by his peers,
He's the only one who can see the transaction (
or users with old client), that's why it's not visible in blockexplorers.
After he updated the client and abandoned the Tx, he created a new standard transaction as written in his last post.