Ok guys,
Assuming that guy looked educated (well, he did know his guitars), he's probably a smart guy, and you guys DO know he will probably be a little worried and can easily do some googling if anyone might be talking about him?
I searched "Guitar shoplift singapore" and this post is right on top, along with 3 more other posts.
(He's probably seeing all these posts and planning how to remain eluded, but)
So, anything you say here, he'll take into consideration.
Hey Mr shoplifter,
I hope you sleep well with what you did. If shoplifting is fine in your mind, taking something that's not yours, and thinking you deserve the guitar, it'll just be the start of the rotting of your soul and morals (if you have any). God forbit someone do something horribly similar to your own possessions or something more valuable.
And by the way, may your children have no backside.