Are you certain they were not placed in your Bonds pouch? That's where they usually end up and you can withdraw it from there. This should help:
Unable to find RuneScape Bonds
If they are not on your account at all, make sure you didn't accidentally purchase OSRS bonds if you intended them for use for RS3. If this was the case, or if you did make sure it was RS3, you would need to get in touch with Jagex's Billing Dept. The page linked has the "Contact Us" link.