Comment 4 for bug 1165461

I'm not in charge of the bug, but if your problem is missing passwd information, then the behavior of PAM might be correct.
PAM is supposed to handle authentication only, NSS is the responsible part of getting user's info.
You might have a closer look to:
a) nscd, to cache users' info
b) SSSD (System Security Services Daemon), that is included in Ubuntu, to allow NSS information to be propagated and locally cached.
My eur 0.01