Problem with using a variable in a controller from a Visualforce page

My problem is as follows:

I've got a Site VF page with fields bound to a custom Lead object. One of these fields is a id field that's used for contact lookup. The controller seems to work fine but all records created with it are empty, since the lookup in the controller code returns 0 rows.

This is the controller:

public with sharing class VF_TabletWaitingList {

    private final CustomLead__c sales;
    private Contact c;

    public VF_TabletWaitingList(ApexPages.StandardController stdcontroller) {

      this.sales= (CustomLead__c)stdController.getRecord();
    }

    public PageReference createNew()
    {
        //CustomLead__c solumal = new CustomLead__c();
        //Set the record type on CustomLead
        RecordType r = [select Id 
                        from RecordType 
                        where Name = 'Verslun' 
                        AND SobjectType = 'CustomLead__c' limit 1];
        solumal.RecordTypeId = r.Id;

        try{
            Contact c = [select id, tx_Id__c 
                         from contact 
                         where tx_Id__c =: sales.tx_Id__c limit 1];
            system.debug('Id: '+c.tx_Id__c);
            sales.Contact__c = c.Id;
        }
        catch (Exception e){
        }
        try{
            insert sales;
            system.debug('Inserted'+sales.Id);
        }

The debug log for the Site user shows this:

09:54:31.059 (59258000)|SOQL_EXECUTE_BEGIN|[25]|Aggregations:0|select id, tx_Id__c from contact where tx_Id__c = :tmpVar1 limit 1
09:54:31.076 (76765000)|SOQL_EXECUTE_END|[25]|Rows:0

I thought it would be enough to refer to the sales object like I do in the standard controller. Any ideas where I'm going wrong?