Why hasn't this cartoon been released?

It's the second of five cartoons Warner Bros did with these characters. The full list consists of:

The Curious Puppy (1939)
Dog Gone Modern (1939)
Prest-O Change-O (1939)
Snow Time for Comedy (1941)
Dog Tired (1942)

I used to really enjoy these cartoons as a kid in the 60s, when they were aired all the time on television. Now they have become exceedingly rare, even on the internet, where all copies of them have been hunted down by Warner, their rights asserted, and removed from view. But why, if none of these have been released? They deserve to be seen again.

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