Q: restrictions passcode

If you have forgotten it then it cant be found anywhere.

If you forget your passcode, you must restore the iPhone software. You can use iCloud or iTunes to restore iPhone from a backup.

Restore from an iCloud backup: Reset iPhone to erase all settings and information. Sign in to iCloud and choose Restore from a Backup in the Setup Assistant. See Reset on page 138 of manual.

Restore from an iTunes backup: Connect  iPhone to the computer you normally sync with, select iPhone in the iTunes window, and click Restore in the Summary pane.

OR

You will need to place the Device into Recovery mode...

And All Data will be erased...

http://support.apple.com/kb/HT1808 , http://support.apple.com/kb/HT1414     http://support.apple.com/kb/HT1808

You don't. You either remember it or restore your phone as a new device in iTunes to remove it. There is no way to retrieve it.

Do you have a Mac?

Perhaps you missed that the OP is talking about the Restrictions passcode & NOT the iPhone passcode.

Restore your phone as a new device in iTunes...hit the Restore button on the Summary pane. When finished, eject the phone.

TA

You're welcome.

Yea the passcode