From what I can tell, this is a rare occurrence where Play/App store approve a transaction, but the transaction is not updated/validated in the IAPHUB database.
The IAPHUB documentation on this is
The purchase has been successful but we need to check that the webhook to our server was successful as well. If the webhook request failed, IAPHUB will send you an alert and retry again in 1 minute, 10 minutes, 1 hour and 24 hours. You can retry the webhook directly from the dashboard as well
The suggested way to handle this is to make a modal window that says something like
Your purchase was successful but we need some more time to validate it, should arrive soon! Otherwise contact the support (firstname.lastname@example.org)
For the exact scenario, I would assume this is a rare occurrence where IAPHUB and the Play/App Store have a communication problem between the two of them.
From everything I have read, you will be safe to treat this as SUCCESSFUL purchase.