Partial db dump/restore
How about trying to solve this problem with Point-In-Time-Recovery? A dump has the problem that you got an old set of data anyway. I highly suggest to use a backup method giving you ways more recent version of the data.

You can also write yourself a simple change-log trigger storing all the information which has changed in a simple table. Here is how it works: http://www.cybertec.at/tracking-changes-in-postgresql/
The code in the site should give you a rough prototype and help you to fix things.