I created a 'Image from Folder" using Disk Utility, with Encryption and Files are Invisible
The 'Image from Folder' will use the existing ownership/permissions of the folder and files.

First off, is the disk image a read/write image?  Are you able to add new files to it?  If not, the instructions below won't work if it is read-only.

The permissions you've listed, "-rw-r--r--@", mean that the file is read and writable by the owner and readable by everyone else.  The @ at the end means there are extended attributes to the file, which might include some kind of invisibility option.  You would have to get a directory listing with -@ to show the attribute keys.
For example, here is a listing showing an image that I manually set to be hidden.

$ ls -l@
-rw-r--r--@ 1 insom  staff  - 64832 Dec  6 18:56 FunnyImage.png
    com.apple.FinderInfo       32


If all your files also have a com.apple.FinderInfo attribute, use Terminal to change into the directory of the files and run the following command to unhide the files.

chflags nohidden *


Now, if your dir listing doesn't show the com.apple.FinderInfo attribute then they are not being hidden using this method but something else is going on.

Have you tried rebooting?  What about copying the disk image to a different computer and mounting it?