SuggestField Add-on

Hi, I am using the SuggestField Add-on and I am quit satisfied with it. But now I have a little problem, probably soemone can tell me the reason: If I set a value it is not displayed in the field but it has been set. I think the reason migtht be an error in my code, I hope someone can give me an advice:

public OrganizationCustomerSuggestionField(Organization organization, OrganizationCustomerType organizationCustomerType) {
        this.setLocale(UI.getCurrent().getLocale());
        this.setImmediate(true);
        this.setInputPrompt(Lang.getString("playerSearch", getLocale()));
        this.setWidth(100, Unit.PERCENTAGE);
        this.setNewItemsAllowed(false);
        
        //
        // Set the suggestion handler
        //
        this.setSuggestionHandler(new SuggestionHandler() {

            /**
             *
             */
            private static final long serialVersionUID = 5936331305246105024L;

            @Override
            public List<Object> searchItems(String query) {
                organizationCustomers = OrganizationCustomerUtils.searchForName(organization, organizationCustomerType, query);
                
                List<Object> results = new ArrayList<>();
                for(OrganizationCustomer customer : organizationCustomers)
                    results.add(customer);

                return results;
            }});
        
        //
        // Create suggestion converter
        //
        this.setSuggestionConverter(new SuggestionConverter() {

            /**
             *
             */
            private static final long serialVersionUID = -8342054010047293L;

            @Override
            public SuggestFieldSuggestion toSuggestion(Object item) {
                // TODO Auto-generated method stub
                SuggestFieldSuggestion sug = new SuggestFieldSuggestion();
                sug.setId(((OrganizationCustomer) item).getUser().getPid()+"");
                sug.setDisplayString(((OrganizationCustomer) item).getUser().getSurname().toUpperCase()+" "+((OrganizationCustomer) item).getUser().getFirstname());

                return sug;
            }

            @Override
            public Object toItem(SuggestFieldSuggestion suggestion) {
                for(OrganizationCustomer customer : organizationCustomers) {
                    if((customer.getUser().getPid()+"").equals(suggestion.getId()))
                        return customer;
                }
                return null;
            }});
    }

Thank you,
Florian