Sound Block disappears from .blend file after saving twice (bug?)

Curious to see if this is a bug or something I’m doing wrong (I am a blender noob; using 2.47 in Windows):

(1) Click on “Sound Block buttons” button [from “Scene (F10)”]
(2) Add a wav file; name the object “MySound” (or whatever you want)
(3) Save the .blend file; close blender; reopen the .blend file
(4) Sound block object name is now in red, but is still there (you can hit the play button) [I haven’t been able to find what the red might mean, but it’s ominous…]
(5) Save the .blend file (having made no changes to it!); close blender; reopen the .blend file
(6) Sound block object is now gone! (wtf?)

Interestingly, if you add two sound blocks, you can make the red coloring in step 4 disappear by toggling between the two sound blocks (using the pulldown to the left of the sound object name). If you make the red disappear like this, the object doesn’t disappear after saving.

Am I doing something wrong, or is this a bug?

Pardon me if this is the wrong place for this question. If it is a bug, please let me know where to appropriately report it.

In Blender unused data is automatically deleted if the file is saved, reopened and saved again. It works the same for meshes, material, textures, sounds, etc. To prevent the sound from being deleted, just add a Sound Actuator that uses that sound somewhere.

Note that most of the time, there is a ‘F’ option that lets you prevent Blender from automatically deleted unused data, but this isn’t present for the sound blocks.