Thank you for posting regarding the issue you are having with a gem purchase. If the purchase does not appear in your purchase history then the transaction was not complete. You may want to try contacting iTunes Support iTunes - Contact Us - Apple Support or Google Play Support Android apps & games - Google Play Help to see if the transactions are pending or if there is another issue with the purchase.
We can recommend un-installing/re-installing the app if there is an issue with the install itself. Also, check the WiFi or 3G/4G bar status on your device to see if a strong signal is received in the event there was a drop in connection while the purchase was being made.