Search in memo some string

Hi all!

I have a problem, when try to setup query like this: 

Table: xkt:workflows

XML memo contains ‘<GroupGuidType_operation="none" externalGuid="5d0db763-4191-e664-ad08-de26b2a3faab"/>’ 

My query returns 1 result ( only the current workflow where the search is being made ), but I know for sure there should be more results. 

what am I doing wrong? The workflow I am looking for contains this string (I took the text from the downloaded package)