If ever you found out that you are missing a sphere and is definite that you previously owned one, there is a big possibility that you may have sold it for Zel.
If the sphere is important to you or is a part of your main team's gear or squad set-up, you can file for a request to restore it. Just be reminded that there is only a limited amount of restoration possible per account and the case will still be subjected for an investigation. If you were able to reach the limit, no restoration request will be entertained.
We are implementing a basic rule for sphere restoration, only unique spheres will meet the possibility of restoration; they are spheres that are only attainable once and/or unique in an account. Such spheres for example are Drevas and Dandelga. Please be reminded that the Brave Frontier Team will not entertain such other sphere restoration request, which are readily available and attainable in the game such as through crafting or forging.
Disclaimer: The Game Support team will only entertain this kind of concern within a limited amount of time or days, which is seventy two (72) hours or three (3) days starting from the time or date of occurrence. The reason for this is if a lost sphere is important to you it is imperative that you report it to us immediately since it is the players responsibility to take care of their respective accounts.. We are reminding everyone to be very careful and be aware of this provision.