How to fix Soft 404 error after threads are merged?

[induslady]

Hello,

In my forum two threads were merged-
http://www.indusladies.com/forums/te...1082-test.html
was merged into this thread:
http://www.indusladies.com/forums/te...4251-test.html

Now when the old thread was accessed it shows a soft 404 error. Why isn't a permanent 301 redirect set for the old thread after it was merged with the new thread?
Please clarify.
Thanks in advance for the support and response.