There are two ways refunds are shown in Barclaycard online servicing. When you're on the 'Summary' page, refunds under the 'Recent transactions' header, have a green arrow next to them.
On the Transactions page, the refund will have CR next to the amount, e.g.
Joe's Store £10.50CR.
The date of the refund will be the same as the original purchase, rather than the date of the refund.
If you've been expecting a refund but haven't received it, you can find more information here.