They are probably on the DLQ. You can configure a number of retries before the message goes towards the Dead Letter Queue.
You probably need to consume those messages on the DLQ. of if you have a testing environment, maybe you should just reset your DB.
You were right and i was totally blind :-(
The Messages were in the DLQ. I wrote a little program that pulled them out of the DLQ and just resend them, as you suggested.
Can you send me the little program you wrote to resend DLQ messages?