From the Home screen open Media.
Hit the menu key and select Explore.
Select Media Card, then Blackberry, then pictures.
Hit the menu key and choose Show Hidden.
Highlight the hidden pic, hit the menu menu key select properties.
When the properties window open, select Hidden and remove the check box then hit Close.
Open Media folder > Menu > Explore > find the folder you have the file in > Menu > Show Hidden... you might want to use Menu > View Thumbnails... this will help you see the images... the hidden ones will be slightly dimmer grey outline.