If it didn't throw an error then it sent the message. The fact that the message wasn't received doesn't mean it wasn't sent. It could be rejected on the receiving end for various reasons. Just as google didn't work because of relay restrictions on their end the same can be true of the receiving end.
As I mentioned before I will soon be adding db storage of the contact form submittals so messages can be received even if mail fails for any reason.
Best Regards,
Joe