Law school admissions isn't that through they will see an F it will not look good, but they care about the numbers and LSAT. If you want to right an addendum explaining the F you can, but with a 3.3 you can get into numerous schools with a decent LSAT score.
I got a D and a W one semester went to law school, graduated, passed the bar, etc and there was no rough patch I was just lazy as a 19 year old sophmore in college. I was accepted to numerous schools despite that my LSAT and overall GPA were sufficient to get admitted.
Certainly avoid F's and W's they will not help you, but your chances of getting into law school are not ruined.