Accidentally Violated Ap exam and I wasn't caught?

Hi there. I took ap English language essay and I did well enough to get at least a 5. There’s a slight problem… On the FRQs I used a highlighter to underline important quotes I would use on my essay. Our proctors had no clue that highlighter wasn’t allowed and didn’t even notice/ care that I used a highlighter. I only found out because my friend said it wasn’t allowed. The only way they can tell if I used a highlighter is if they open the packet that I sealed up for the frq. I am really concerned that they will invalidate my test. The question here is: could my exam be invalidated?

I browsed the AP exam policies here:

Highlighters are indeed not allowed, unless they are pre-approved as accommodations for disabled students.

However, it is unlikely they will open the test booklet and see.

Unfortunately, I cannot tell you what you should do, but have provided futher information to help you with your decision.