you just cannot sue them for additional damages if they did, in fact, make that due diligence
What does "due diligence" mean.
Hoping not to lose you guys here but I spent a few years studying law. No law degree though. And what I saw will scare you.
First legal terms only vaguely resemble, in meaning, the common usage meaning. That alone better make you redouble your efforts on anything legal. And legal definitions are much more strict in how they are applied.
But what is due diligence. In law almost every legal action that one would wish to take against another requires that the other be served and give a minimum amount of time to respond. There are times when it is 30 days other time as little as 3 days. I have seen cases were the law firm would print the letter with the day it was written date and then hold the letter till a day or 2 before the response was required. Or for the more reputable they would mail it on saturday.
So what exactly is due diligence. It could be as little as printing a notice in paper of record. Translated, the town Middle of Nowhere has a newspaper and they put the notice in there looking for the copyright owner of any given work. Meaning the copyright holder will never see it.
Now all that is the extremes. But none the less if some wants to, unless that due diligence is much more clearly defined, they may be able to steal your work and make it so you can never recover damages. So it is all really in the exact wording and how a lawyer and his judge buddy interpret said law.
I don't wish to be an alarmist but what you see and what they see are 2 different things.