How to Regain 'Lost' User?

[Jud]

Was puttering along changing shells from sh to zsh for root and user, using chpass -s.  This went off without a hitch for root.  Then unaccountably (typo?), when trying the same for user, I received a response that the user was unknown.

When I try to create a new user with pw, I'm told a user with this name already exists.  When I try to delete the user, I'm told there is no such user.  Same with sysinstall - gave an error (74) when I tried to
(re)create the user.  I've also attempted to delete the relevant entries from the passwd, master.passwd and group files.  After those deletions, trying to add a user with sysinstall or pw results in an error message about user being dropped or lost during the operation (sorry, can't remember the exact wording as I sit here on lunch break).

So rather than continuing to flail about, where should I look for information about what to do?
 
Thanks,
 
Jud