Dear nomolo,
Thanks for bringing this to our attention!
I have good news and bad news. Bad news first: there is no way to prevent Disk Utility from showing these disk images while the folders are unlocked.
The good news is that you *can* clear this list after folders are locked, and you can do it right now without waiting for us to update Espionage to automatically do it.
Simply use
Platypus to create an application that runs the following command:
defaults delete com.apple.DiskUtility DUSavedDiskImageList
Put that command in the script it runs, and export the thing as an application bundle. Then for all your folders, add a folder action to run that app every time you lock a folder. This will clear the list of disk images from that preferences file.
We'll make sure to add this to the next update so that Espionage automatically does this for you.
Remember: plausible deniability is very hard, and as you notice, just one leak is all it takes to reduce it, so it's a never ending battle.