Maybe the freelancer is dead.
It really does not matter if Upwork provides you with additional contact information or not. You are not going to be able to sue this freelancer or get money from her.
You own all of the work that you have already paid for. You may share all of those files with the other members of your team and/or the new people you hire to continue the work.
If you feel that your product manager or project manager failed to obtain and archive usable files during the course of that freelancer's work, then that is something you should take up with them. You may need a course correction with regards to how you work with freelancers and work files.
If a freelancer is doing work, then it is possible to obtain those work files DURING the course of their work. If you hire any freelancer using an hourly contract, then ALL WORK PRODUCT - all files produced - belong to the paying client.
As a freelancer, the first thing I do - whether it is an hourly or fixed-price contract - is create an online shared space where I do all of my work. I provide the full credentials to the server to the client immediately. That way the client has complete access to all the work, all the time. You can insist that the freelancers you work with do the same, or at least provide the latest version of all files on a daily basis.
There should never be any such thing as "not being able to use any of a freelancer's work until the final version."
I really do want you to succeed in your endeavors. I hope you will not hesitate to ask if you have additional questions.
Maybe you need to take a closer look at the work you have already received. You hired a freelancer and paid money to her for an extended period of time because you liked her work. She was sending you initial versions of design that fit your vision of the project, which is why you continued to pay her as she logged over 100 hours of time. I understand that you wanted further revisions, but you can use the latest version that you have. And if you want further changes, other professionals can carry on the work that the original freelancer started.
As a project owner or project manager... turnover of key personnel isn't what we want to see happen. But sometimes it does happen. It doesn't mean that the project is doomed to fail. You have probably seen The Wizard of Oz (1939). One of the all-time classic movies. It had FOUR different sucessive directors: Richard Thorpe, George Cukor, Victor Fleming, and King Vidor!
I think your project can succeed to, but only if you make your project your top priority, ahead of any individual freelancer.
