Image captured and then deleted from gallery. Can it be recovered and get into wrong hands?
Yes, any ordinary deleted data can be restored, BUT...

... many programs delete data like this: They tell the hard drive (flasdrive, etc.) that the deleted area can be overwritten. Aslong you dont fill your diskspace, you can recover the deleted files full or partial. 

What you can do against:

Simply use your smartphone, data will be added, deleted, modified when you do something with it.

Fill your diskspace: Well it sounds nonsense, but it works. Simply move files on your sdcard, or internal storage and fill the disk space, than delete them. The old data is finally gone.

Greetings,
Fischmaster