By the way you have phrased your question it appears that your son's grandmother's Will has been presented to the Court for probate - a proceeding by which a will is proved to be valid or invalid.  The proceeding is filed in the County his grandmother lived when she died.  Start by going down to the Surrogate's Court (the court specifically for wills, etc.) in that County and look up her name and the court filing number (called an index number) and ask to see the file.  The executor has an obligation to explain to the court where the money - which is called as asset of the estate - has been placed.  It is assumed here that you are the child's legal guardian and should have been notified of his inheritance.  If this gets you no where it may be helpful to hire a lawyer to contact the executor on your son's behalf.  Look for one on this cite that does Estate work.