Does evaporation reverse salt hydrolysis?
Simple cyanide salts

In aqueous solution, simple cyanide salts more or less completely dissociate into their constituent ions.  E.g. for potassium cyanide:

$\ce{{KCN}(s) + H2O(l) -&gt; K+(aq) + CN- (aq)}$

Those solutions are relatively stable.  There is an acid-base equilibrium between $\ce{CN-}$ and $\ce{HCN}$, but in unbuffered or in alkaline aqueous solution this equilibrium will be almost completely on the left:

$\ce{CN- + H2O &lt;&lt;=&gt; HCN + OH-}$

Over very long times, if the solution is left in an open container, some of the tiny, minute amount of $\ce{HCN}$ formed in this way could evaporate, leading to a very slow loss of cyanide from the solution.  If stored closed this will not be a problem.  

(Mixing simple cyanide salts with an acid will result in an immediate and dangerous release of gaseous $\ce{HCN}$, so in this question I assume that no acids are involved.)

Thus, for simple cyanide salt solutions stored appropriately, yes you should indeed be able to recover all of the initially added the solid salt after boiling off or otherwise removing any water.

Cyanide complexes of transition metals

Salts such as potassium ferricyanide $\ce{K3Fe(CN)6}$ consist of potassium cations and complexed ferricyanide anions, $\ce{Fe(CN)6^{~3-}}$.  They are soluble in water as well, but unlike their simple cyanide anions, they can be hydrolyzed. 

The hydrolysis is catalyzed by UV light and results in the formation of free $\ce{CN-}$ anions as well as iron hydr(oxide) solid precipitates.

See this book for more information.