I'm sorry that happened to you. This can indeed be very frustrating but can also happen in rare cases.

If you're playing on an iOS device, please go to the game settings, accessible from the main menu. There you should find "Restore last Purchase". Please tap on it and enter the same details as you did for your purchase. If you're using the same Apple ID, you will receive your last purchase at no additional cost.

However, if you're playing on an Android device, you just need to go into your device settings. Please make sure you're connected with the same Google Play Services account you used for your purchase. The next time you start BitLife GO!, your last purchase should be restored.