Async Search: getAsyncResults returns nil?

I'm dipping my toe into async web services calls and have run into a snag.  I'm performing a search with the following call:

<soap:Envelope xsl:version="1.0" xmlns:tranBank="urn:bank_2008_1.transactions.webservices.netsuite.com" xmlns:generalComm="urn:communication_2008_1.general.webservices.netsuite.com" xmlns:platformFaultTyp="urn:types.faults_2008_1.platform.webservices.netsuite.com" xmlns:actSched="urn:scheduling_2008_1.activities.webservices.netsuite.com" xmlns:setupCustomTyp="urn:types.customization_2008_1.setup.webservices.netsuite.com" xmlns:listAcctTyp="urn:types.accounting_2008_1.lists.webservices.netsuite.com" xmlns:tranSales="urn:sales_2008_1.transactions.webservices.netsuite.com" xmlns:tranPurch="urn:purchases_2008_1.transactions.webservices.netsuite.com" xmlns:listMkt="urn:marketing_2008_1.lists.webservices.netsuite.com" xmlns:listSiteTyp="urn:types.website_2008_1.lists.webservices.netsuite.com" xmlns:listEmpTyp="urn:types.employees_2008_1.lists.webservices.netsuite.com" xmlns:generalCommTyp="urn:types.communication_2008_1.general.webservices.netsuite.com" xmlns:listRel="urn:relationships_2008_1.lists.webservices.netsuite.com" xmlns:actSchedTyp="urn:types.scheduling_2008_1.activities.webservices.netsuite.com" xmlns:tranBankTyp="urn:types.bank_2008_1.transactions.webservices.netsuite.com" xmlns:platformCore="urn:core_2008_1.platform.webservices.netsuite.com" xmlns:listSupport="urn:support_2008_1.lists.webservices.netsuite.com" xmlns:tranGeneral="urn:general_2008_1.transactions.webservices.netsuite.com" xmlns:tranCustTyp="urn:types.customers_2008_1.transactions.webservices.netsuite.com" xmlns:xsi="