There is no communication from/integration between 2sms and Discovery. The receipt status of a text message is not communicated back to Discovery.
In order to check your text status information, you need to log into the 2sms web application. www.2sms.com/login.aspx
Use your 2sms login credential (username/password) issued by 2sms.
Goto Reporting>Outbound>choose a date range