One of my contractors issued me a refund on the 13th. He sent me a screenshot confirming this, however it is now the 29th and I've received no refund nor have I received any email confirmation stating there is a refund in progress.
Is this normal? How long does a refund normally take to process?
Refunds are subject to the standard 6-days security period as well. I have checked at it looks like you received a refund on May 18. You can check it yourself by going to Reports > Transactions. Is it the refund you are inquiring about? Also, note that when a freelancer refunds, the money go to your Upwork account and can be used for future payments.
I hope it helps.