You come up with a discovery plan that both parties can agree with (or one that's imposed by the court). You figure out the scope of the search (which DBs, hard

You come up with a discovery plan that both parties can agree with (or one that's imposed by the court). You figure out the scope of the search (which DBs, hard drives, phones, etc.), the search terms to run, etc. You do depositions of employees to figure out who and where else potentially relevant documents can be. Obviously you can't prove a negative, but you end up doing an exhaustive search.