CNA2RN2014

I am a full time nursing student (about to graduate in May, God willing) and I work at the local hospital PRN as a CNA. They are fully aware that I am a nursing student (RN) and that I normally pick up shifts on Friday evenings and weekends when I am able. I called the staffing person earlier this week to pick up a shift for Friday 2nd shift (which I normally do) and she said that she put me down for it. Somewhere in the confusion, she put me down for Wednesday 2nd shift instead of Friday. I had no idea that this happened until they called me an hour after I was supposedly scheduled to ask why I wasn't at work. They also had me down for another floor on Thursday evening which I didn't know anything about. I get a call asking why I wasn't at work from the staffing person. I told her that I did not say Wednesday, that I said Friday 2nd shift and that I am not able to work during the week because of school! She kind of got snotty with me and she said that I said Wednesday. The charge nurse on the floor called me to ask if I knew I had to work today. I explained it to her that I had already talked to the staffing person and there was a misunderstanding with scheduling. I apologized whole-heartedly for this misunderstanding in scheduling. She didn't really say anything except that she had to call somebody on how to handle this. Either way, I did not go in today so they put me down as a call out on the online schedule. I have a good rapport at this facility, never called in sick, I am NEVER late (I am usually the first CNA there on my scheduled days), and I am a hard worker. A lot of nurses have told me that I am the best CNA that the floor has. I just hope that this incident doesn't come back and bite me in the butt because I really want to work there as an RN when I graduate this year. How should I deal with this situation? PS- I have 2 witnesses that were with me when I initially spoke with the staffing person when I picked up the shift and they both said that I said FRIDAY and that I never mentioned working on WEDNESDAY.