How do I track missing Apple Pay refund status?

Contact the merchant and request the Acquirer Reference Number (ARN). Every refund to a credit or debit card must be issued and ARN. Give the ARN to your bank and request they trace the refund.

I suspect the merchant has not released the funds yet.

Re: "Refund processed but never received": " ... on Apple Pay it shows in my balance I was refunded as the money was added in my account but it’s not there ... ", "... so where is the money at?"

Apple Support's article:

Get a refund for purchases made with credit or debit cards using Apple Pay - Apple Support

Eg: says:

"When the merchant processes your refund, it goes back to your payment card automatically, but it might take several days to appear on your card statement."

More info. if needed: How to: Track orders and purchases in Apple Wallet - Apple Support

and

Apple Pay Support website (info. / support / contact options etc.): Apple Pay - Official Apple Support