database owner gone?

we have a problem here at a large database using postgresql.
i used it with no problems yesterday and suddenly today all
the databases were no longer visible in phppgadmin.

using pgsql -U admin <database> does give me access.
so i thought something was wrong with the usersettings. checking
these settings with \d reveales that the table no longer had
an owner.

select * from pg_user gives me only 1 user (postgres). pg_shadow
also gives 1 user. so i tried recreating the admin user with
createuser admin (as postgres user) but that failed saying admin
allready exists! so where is it now? and how do i get access
back to my database using pg_dump and phppgadmin?

thanx for any help,
Evert