Source: The Great Interpretation of Dreams (Ibn Sirin)
Losing a ring in a dream indicates the loss of kingship or authority, or divorce from the wife, or death of a child.
Source: Perfuming Humanity in the Expression of Dreams (Al-Nabulsi)
Losing a ring indicates losing something dear or loss of money.
Source: Signs in the Science of Expressions (Ibn Shaheen)
Losing a ring is interpreted as worry and calamity.