Searching for an Empty Field

Searching for an Empty Field

I'm trying to use the CRM api to search for Leads that have no value in one of the custom fields. Since the field is a URL field, I figured an easy way to check for an empty field is using the following API call:

https://crm.zoho.com/crm/private/json/Leads/getSearchRecords?authtoken=TOKEN&scope=crmapi&selectColumns=Leads(Channel Name)&searchCondition=(Channel Link|doesn't contain|http*)

I update the link field myself, so I that know if it has a value it will begin with "http".

However, the issue I am having is that if the link field has not been previously edited, it will not show up in the search results. For example, if I create a new Lead and don't add anything to the link field, then when I run the search, the new lead does not appear as a result. However, if I go into the lead, click edit and then click save without typing a value, then it suddenly does appear in the search results, even though in both cases the value was empty.

Is this a bug? Does anyone have a workaround, or know a better way to search for all records with no value in a given field?