This is a case of poor organisation and communication.
The department that assigns Raman field duty should be organised. Ensure that Raman has some advance notice before asking for extra duty, ensure that as Raman is not parmanently based in this department, it knows what his schedule is before assigning someone who has been on night duty work in the morning however urgent.
Raman is not organised him self and has no communication skills. he should be able to communicate that he is on night duty and working in the morning after night duty is a problem, proactively he discusses a favourable time to do the field duty. Family is important, but not at the expense of the job. Many people have families but no jobs so therefore jobs may have an upper advantage when it comes to priority. Raman should have asked someone else to help with the sick person or in the case there is no one to help, he should explain to the supervisor (not HR) that he has a family problem.
Personally i discourage sms as a means of communicating officialy, email or face to face is better. someone will claim your sms did not arrive and you will have no proof of having sent it. sms can only be sent if all other means have been exhausted.
Loyalty is a competence when in the palace with a king or queen, loyalty is not a competence in the organisation of today. Instead proactive organisation and communication, getting results (execution), knowing how to do the job (technical competence), team and self leadership and interpersonal relations are higher competencies. This means that Raman should be sympathised with because he is loyal.
While Raman should have been given a chance to explain, he would have been given a chance to give excuses of his failure to be organised and while these are strong for the individual, they are not strong at all for an organisation that has to compete with tough companies in order to make return on capital and pay workers like Raman.
My advice for us is that always inform the boss before you get into a problem, your explanation should not be excuses. Excuses is when one blames something or someone for ones failure. We are instructed to use our resourcefullness and initiative to overcome challenges....loyalty is not a resource, being able to communicate is a resource.