score:6
Originally the mosaics probably survived, Fergusson writing:
The frescoes and mosaics have, indeed disappeared from the body of the church, hidden, it is to be hoped, under the mass of whitewash which covers its walls--in the narthex they can still be distinguished.
A History of Architecture in All Countries by James Fergusson (1874), p.442.
However, during the Russo-Turkish war (1875-1877) the building was used to house Bulgarian refugees and became a ruin during which time the roof was not maintained and heavy water damage to the ceiling artwork occurred. Also, the refugees and other vagrants vandalized the interior. During restoration in the 1890s, additional removal of artwork, some of which was heavily damaged, occurred.
It is likely that at least some limited amount of the artwork remains in particular areas under the plaster.