I'm not sure how you would go about getting your $$$ back, that would be for the mods here to answer.
But for future reference; I would NEVER release payment of funds beforehand. Use Upwork's escrow system and just the milestones and release payment as the project goes along.
Yes - once bitten... That's twice I've done that - first and last.
Althought no sooner had I posted that and I got a msg from the FL to say that things were in progress[??] Let's see what that looks like.
re: "How do I validate a freelancer? I was asked for a payment at commencement, that was released... and now silence"
Regardless of what is going on in this situation, there is no reason to make an up-front payment on Upwork.
Contractors who do hourly work are automatically paid based on the number of hours of work they do.
Contractors who work on fixed-price contractors can work after you fund a payment, which demonstrates that the money is available, but you (the client) are still in control of the funds. The payment is not released to them until they submit the work and you approve payment. But if you just disappear and do nothing, then they'll get paid automatically.
This system works fine for both clients and contractors.
And it means you do not need to make up-front payments, and you really should not make up-front payments.
Making an up-front payment to a contractor you don't know and trust leaves you vulnerable to a contractor simply taking the money, doing nothing, and then disappearing, and then there is little or nothing you would be able to do to get your money back.
Please continue communicating with your freelancer and do contact Customer Support if you have a hard time contacting them. Going forward, please follow Lindsey's and Preston's advice, and use Upwork's Payment Protection Programs and advice we've shared here (and in the linked Help articles).
Please note that due to the time difference and other legitimate circumstances, users are advised to allow a bit of time for the other party to respond.