This will depend entirely on the employment contract your friend had with the organisation and local employment law (I'm not in the US and I'm not a lawyer) but in most cases work done by an employee is entirely the property of the organisation, and they can do what they like with it. In many cases the employer will not only own the copyright to the employee's work but the employee will also have waived the moral right to be identified as the author of the work.
Assuming a watertight employment contract, the only possible get-out I can see for your friend is if the original publication of the document included a copyright preamble with "the moral right of the author has been asserted" or similar, but that seems unlikely.
This may seem a little harsh, but from the employer's perspective it could make sense to list your friend's replacement as the author if they are now in the same post and responsible for the content of the document. In product documentation for instance it's often more important to list the person currently responsible for keeping that document up to date than the person who originally authored the document, though it's more usual to add new authors without removing old ones.
This ownership of employees' intellectual property can even extend to IP created outside work hours. I've not come across it in the writing sphere, but in research jobs in both the public and private sector you need to be careful about inventing things in your spare time in case your employer ends up owning the patents.