I am trying to create a VF page that will allow me to query related records and use the list as options for a VF page Picklist.  I got it working but when I add a where condition to my Query I get this error "Content cannot be displayed: SObject row was retrieved via SOQL without querying the requested field: Package__c.Client_Workbook__c"  I am not sure why it does not accept my where clause.  Can someone let me know where I went wrong.

public class PackageSignInstanceJunctionController {      
    // Constructor
    public PackageSignInstanceJunctionController(ApexPages.StandardController controller)      
        //master
    {
         
        this.proj = (Package__c)controller.getRecord();               
        this.clientWorkbook = proj.Client_Workbook__c;
        this.junction = [ SELECT  t.Package__c, t.Sign_Instance__c, t.Name, t.Id, t.Record_Type_Name__c, t.CreatedDate
                         FROM Package_Sign_Instance_Junction__c t 
                         WHERE t.Package__c = :proj.Id ORDER BY t.CreatedDate Desc];
   
    //Picklist Options
    
    signTemp = [Select s.Name, s.Id From Sign_Instance__c s  where Client_Workbook__c = :clientWorkbook];          
            signList = new List<SelectOption>();            
            for(Sign_Instance__c temp : signTemp)
            {
                signList.add(new SelectOption(temp.Id, temp.Name));
            }   
 }       
    // Insert new Staff junction
    public pagereference insertmethod()
    {
        Package_Sign_Instance_Junction__c cc= new Package_Sign_Instance_Junction__c();
        cc.Package__c = proj.id;
        insert cc;
        return null;
    }
    
    public Package_Sign_Instance_Junction__c[] getjunction() { 
        return this.junction;      
    } 
    
    // Action Method called from page button
    public pagereference saveChanges() { 
        upsert this.junction;
        pageRef.setRedirect(true); 
        return pageRef;
    }
    
    // Action Method called from page link
    public pagereference newjunction() { 
        Package_Sign_Instance_Junction__c d = new Package_Sign_Instance_Junction__c();
        d.Package__c = this.proj.id; 
        junction.add( d );
        getjunction();
        return null;
    } 
    
    public pagereference DeleteAccount()   
    {      
        // if for any reason we are missing the reference       
        if (SelectedAccountId == null) 
        {               
            return null;      
        }
        
        // find the account record within the collection      
        Package_Sign_Instance_Junction__c tobeDeleted = null;      
        for(Package_Sign_Instance_Junction__c a : this.junction)       
            if (a.Id == SelectedAccountId) 
        {         
            tobeDeleted = a;          
            break;       
        }
        
        //if account record found delete it      
        if (tobeDeleted != null) 
        {       
            Delete tobeDeleted;      
        }
        pageRef.setRedirect(true); 
        return pageRef;
    }        
    
    // class variables
    PageReference pageRef = new PageReference(ApexPages.currentPage().getUrl()); 
    public List<Sign_Instance__c> signTemp = new List<Sign_Instance__c>();
    Package__c proj;
    Package_Sign_Instance_Junction__c[] junction; 
    Sign_Instance__c[] sign;
    public string SelectedAccountId { get; set; }
    public string clientWorkbook { get; set; }
    public List<SelectOption> signList {get;set;}
}