SMS will not be considered an official or authenticated form of communication. However, you can send an email from your personal ID.
Alternative Communication Methods
When your reporting person is not picking up the call, you could call his or her subordinate or contact HR. Ask them to inform the individual, stating that you tried to reach him or her and, due to unavailability, you are informing the second in line or HR.
Since it's a two-day leave, do send a detailed SMS to him or her stating that you called and since there was no response, you texted him or her.
There is no harm in the current world. Communication is more important than making excuses.