No, it didn't originally have it. It was added to iOS 4.
I can confirm this is the case due to the amount of restoring/updating/jailbreaking I've done between 3.1.3 and iOS4 and back again over the past couple of days.
The page torn off is not on 3.1.3's icon, it was one of the first things I looked for when I went back from iOS4 to 3.1.3 (before restoring to iOS4 to re-jailbreak it).
Also, Voice Memo's has a tweaked icon in that the "U" shape part of the stand holding the mic is red instead of silver ... looks a bit odd actually.