Okay.
What have you put in place to locate the unaccounted for artworks as fast as possible and avoid this happening again? What compensation or reassurance can you offer the artists whose works were put in your care at a time when they were not worth anything? They actually must not have been very happy that their works were not worth anything. An artist's works are worth something to them. An artist puts their heart and soul into what they create. Whether a work is worth $500 in your eyes or $50,000 in someone else's eyes, that is not what motivates the artist.
What process have you established for recovering these artworks? Regardless of value, it has to be done.
What is your relationship with the artists who have been hurt in this tale?