Don't worry! Let's take a look and see what happened.
A)I've already paid and received a notice that the card was processed, as well as a Google receipt, however I still haven't received the item I purchased:

Please go to the Settings page on the Plant Nanny² main menu and tap Restore Purchases. Look to see whether you have now received the item you purchased. If you still have not, please go to the Settings page on the Plant Nanny² main menu and tap FAQ to contact us. Be sure to include an order number in the form: GPA.1234-1234-1234-12345 with your message to allow us to better assist you!

Note: Please be sure to include your FDID when reporting the issue. For convenience, you can go to Settings > Tap your profile picture > long press on your FDID first to copy your FDID. If you haven't already linked with a social media account, please do so. This will allow us to view the purchase in question and take steps to resolve your issue. If you haven't registered previously and do not wish to register your account, we ask that you instead request a refund for your purchase. For information on how to request a refund, please see here.

B) I've already paid and received a notice that the card was processed, however I haven't received a receipt from Google or the item I purchased:

Please go to Google Play and tap the menu icon > tap Account > tap Order history to see whether the item you purchased is listed. If it does not appear on the list, or if it is listed however you still have not received a receipt or the purchased item after more than 24 hours since the purchase date, please use this page to contact Google Customer Service.

If you are an iOS user please see this tutorial.