A freelancer I have hired, and who has completed the bulk of the project, has become unresponsive. I am going to give him another two weeks to pop back into view and complete the task.
However, if he does not re-appear then what are my options to resolve the issue via Upwork or recover the funds already paid to him?
I'm sorry to hear about the bad experience you've had with your freelancer.
One of our team members will reach out to you via ticket as soon as possible and will assist you further with your freelancer. Thank you.
My advice to you is to understand that this is normal.
An effective client should always plan on having personnel turnover, whether you are running a restaurant or managing a development project online or doing anything else.
A client never needs to wait for or rely on Upwork Customer Support. Clients have all the tools they need at their fingertips, to deal with such situations themselves.
Put very simply... when one of the freelancers on your team is not responsive, then you assign her tasks to other team members.
The important thing is your project. Put YOURSELF first. Do not elevate one individual freelancer to a place of prominence that she doesn't deserve.
re: "if he does not re-appear then what are my options to resolve the issue via Upwork or recover the funds already paid to him?"
If any money is in escrow, then the money will be returned to you automatically after you take the proper steps. This is not a big deal: