I don't see my Zendesk Talk number in my account. Why was my number deleted?
Your number can be removed from your account if your trial expires, your Talk subscription is canceled, or if your Support account is suspended or deleted.
The Talk number can also be deleted if the number is not used for more than 60 days. Zendesk sends you the first warning email after 30 days since the last time the number was used and a second warning after 53 days.
For more information, see the article: How can I recover a Talk number?.