Blackberry video - lock3 file extension question

I retrieved a video file from a memory card from a blackberry 9000. The video had a file extension of .lock3 which i assumed meant it had been encrypted. I attempted to play the video file anyway and was successful. I'm having difficulty explaining why the file extension is .lock3. From what I've read the file should be encrypted. Has anyone come across a .lock3 file that is NOT encrypted? I'm guessing that perhaps the file was encrypted at one point, but I'm wondering why the extension of .lock3 was left on the file.