To all: Please keep in mind that Arena rewards are added to your account when the run ends. In the case of the force-retired run these reports are for, that was the second the expansion released. You might not even have been logged on at that time.
Going to the Arena screen to open your rewards is merely a visual animation to show the rewards that at that point were already added to your account.
That is to be expected, since the gold was already added before you bought those two packs.
See Auto retired arena run showed rise of shadows pack as reward but was not added - #2 by BigHugger-2468 for a longer and more detailed explanation (focusing on the pack reward only, but dust, gold, and card rewards are handled the same).