Last week, I did a computer lab for a class. At the end of the instructions was a script that would verify that everything in the lab was done correctly. At the end of the lab, I knew I had done everything correctly; however, the verification script wouldn't show that everything was done correctly.
The instructor didn't mention that some additional changes would have to be made to all the lab files for the verification script to pass. I found that out by going to the TAs. I have proof that the professor took notice of this error last week only after I had brought it up, and that I submitted the lab on the same day he did so - albeit a few hours later.
However, I forgot to make the necessary change for one of the lab files, for which I was docked 3 points (out of 20).
The professor has thus far refused to give me those points back. Assuming the evidence I have of the professor's oversight and of my same-day submission of the lab satisfies the standard of evidence at the department/university level for a grade dispute/appeal, should I appeal the grade or just let it go?