Further Update on my Prior message:
As far as playing MP3 files, if they are placed in the MUSIC directory or any of its subdirectories, MP3 files play fine and can be opened with any of my favorite player apps on the iPhone; problem resolved.
As far as Encryptstick PC application, I cannot tell how to consistently open files created by this app on the iXpand flash drive. Most of the time the iPhone’s Sandisk iXpand Sync application cannot see the files or subdirectories.
So, perhaps the files are much better encrypted and invisible to any potential intruders or thieves, but also invisible to the owner of the files? Just joking. There must be a way.
Welcome suggestions.