Missing shared libraries: libpcre.so.0 and libpam.so.0

[Andrew B. Young]

Yesterday I found my FC4 system complaining about misssing libpcre.so.0 and libpam.so.0.  The system no longer functions; I can only boot up in single user mode.
1) Any ideas how these got lost?
2) I believe I can just re-installed the RPM's that provide these to get back in business but is there a better path.
3) A long time ago someone showed me a command(s) that checked all RPMs' files against the present installation.  Does anybody know of this to see if other files have gone missing?

Thanks,
Andrew