Scheduled graduate admission interview never occured I have applied for admissions in a Ph.D program in Mathematics. It's a small department at a public university.

Some time ago, I inquired the graduate chair about my application status (he/she was the preferred adviser I've put down on the application) and was told a decision was not yet made. Furthermore, I was asked to attend an interview session, so I agreed.

However, the professor never made contact at the scheduled interview time, nor did he/she reply to my follow-up email (singular). 

What should I do next? I found myself in a difficult position.

Thanks.
I would send another follow up email 1-2 weeks after the first one you sent. Inquire politely, and offer to reschedule the interview. However, do it in such a way that they're allowed to save face. Meaning, phrase things in way that don't inadvertently point a finger at them. It might sound silly to placate egos, but...welcome to academia. :-/ 

If nothing comes from it, I would write this program off. As Astronat said, this is pretty poor behavior, and I would add that it might be indicative of what's to come if you were to be part of that department.