Oh this HAS to be a bug, not a forgotten password!
I just tried this to sort out my wifes iPhone 4 (I was blaming her for forgetting what she set her restrictions code as), and I found the com.apple.restrictionspassword.plist file so I tried the encrypted info you gave, but after the restore, it was actually the code I entered in com.apple.springboard.plist under SBParentalControlsPIN that was the code that allowed my to access the restrictions section in settings and turn Restrictions off.
HOWEVER as soon as I went to Settings>Reset>Reset All Settings (which is what I was trying to do in the first place after I read it may help to speed up the dog slow response of iOS7 on the iPhone 4) I was asked again for the Restrictions Passcode (even though I'd turned Restrictions off at this point) and sure enough, neither the correct code nor 1234 would work! Again!!!
Now restrictions is switched back on again and I can no longer access it.
Somehow I think the settings reset is wiping the restrictions code, then resetting restrictions (defaulting?) to ON. Since there's no SBParentalControlsPIN entry any more to match to, you can never have the correct code.