Hi @Agami edtech,
Welcome to Box Community, and we’re glad to help regain your access to the folder.
Kindly check if you could still access the folder in the Box website. If not, is the missing folder your own or shared folder? If it’s the latter, please contact the folder owner.
Meanwhile, if it’s your owned folder you’re looking for please check out your trash.
Hope it helps, and please let us know how it goes.