Ive had that happen a time or two - especially with people that I did not know. At work most people know that I am HH/deaf so they aren't too mean when it comes to me not hearing them when they are behind me and say 'exscuse me' I just apologize for not being aware and tell them that I am HH/deaf and the best way to get my attention from behind is a light tap on the arm or shoulder. After a while when someone taps me I know it is someone trying to walk by, so we smile and go on about our days.
Ive also been to places like the mall in Ft. Smith and I am sitting on a bench and I have my bags sitting next to me and a woman with a cane came up an asked if she could have a seat- of course this was from behind so I did not see nor notice. Then I saw her walk by and give me an ugly look as if I had intentionally ignored her. I got up said "Ma'am, you can have my seat, I am deaf, so I did not hear or notice you until you moved in front of me."
She apologized for not realizing this and the misunderstanding was cleared up. It wasnt like I was giving up my seat to somone who was 'more' disabled than I am, its the simple fact that she was having difficulty walking and asked if I could share my bench with her for a moment. If I had heard her, I would have not had a problem with it. Being nice can go a long ways, but at the same time, dont allow yourself to get stomped on.