I failed to respond to a potential advisor I know that it's a horrible thing to do. It was a professor at a prestigious University who expressed interest in my ideas. I never responded because severe conflict broke out between me and my family regarding my career choice. And that was a year ago. Conflict is still there but I'm stronger, and I sent a sincere apology to the professor, but I still want to know how bad my situation is if I want to reapply to the same University for a Masters (i don't even dare to hope to work with the same professor).
If it is a coursework masters, then you would have minimal or no interaction with the previous professor, unless the professor is teaching a subject in the Masters. 
If it is a research masters and you are in the same department, then you would be working or at least bumping into the prof at departmental meetings and events. 

Seems unlikely that there would be great animosity. Your circumstances seems very reasonable and most people would not react adversely or take it too personally. I am sure if you are in the professor's department, then you can have a casual chat and smooth over any frustrations. The prof might be able to collaborate or support you in some way as they were previously interested.