[Q] HOOPLA digital-where is content stored? topic

First apologies if this is inappropriately posted.
There is an app out there by the name of HOOPLA digital. find it under hoopla in the play store.
many public libraries use it to download digital content ( audio books , movies , music etc..) to their patrons' phones.
does anyone knows where this app stores the downloaded content?
For the life of me I am unable to find either the file or the folder on my phone where downloaded content is stored although it plays just fine.
using latest Kit Kat on a galaxy S4

Puzzling...