Yes, I did give myself permission to access the forum. Did some further checking and I believe the following quoted Q&A from the 'Bugs Non-Beta release' forum here fits my circumstances:

[] 6.5 is the version:

Threads are vanising if a moderator or admin trys to move a thread. The move does create the pointer but when you click the pointer link it gives you a permission error page and the link is NOT move to the new location.
Help!?!

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[] The developer is aware of this and I believe it has already been dealt with for the 6.5.1 release.

The problem occurs when you have forum keywords that contain non-alphanumeric characters (that includes a space). The software is not supposed to allow you to create "bad" keywords, but it does.

You can repair the problem with some SQL queries:

UPDATE w3t_Boards SET Bo_Keyword=' newkeyword ' WHERE Bo_Keyword=' oldkeyword '

UPDATE w3t_Posts SET B_Board=' newkeyword ' WHERE B_Board=' oldkeyword '

UPDATE w3t_Last SET L_Board=' newkeyword ' WHERE L_Board=' oldkeyword '

where oldkeyword = the current keyword with a space or other illegal character in it.

where newkeyword = proper keyword

(You'll need to run this for each forum that has a bad keyword.)

If the "lost" post does not appear in the proper forum after fixing the keywords, you should be able to find it with a search of the database. It may have ended up in a bogus forum.

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Seems my problem is a bug in addition to being PBKAC because I did add a space in this particular forum's keyword. <img src="https://www.ubbcentral.com/boards/images/graemlins/blush.gif" alt="" />

Now I need to try the fix.

Ythan, thank you very much for your help.