I am reading Ionic Equilibrium by James N. Butler. Using silver(I) chloride in excess aqueous chloride as an example it speaks of several forms: $\ce{AgCl (s)}$ i.e. the ionic crystalline salt, $\ce{Ag+(aq)}$ and $\ce{Cl^{-}(aq)}$ the aqueous ions from dissociation, and finally $\ce{AgCl(aq)}$, which Butler purports to be "dissolved covalent silver chloride molecules as distinct from solid salt or dissolved ions."
Does this "molecule" of $\ce{AgCl}$ really exist in solution? If so, is there a way to quantify the concentrations of this covalent species? Equilibrium solubility product constants seem to give the concentration of the aqueous ions only.