This paper should be immediately rejected by the chairs. Authors reaching out to a reviewer is a HUGE no-no in every conference & journal I've ever worked with. I would be shocked if it's not the same for AAAI. If the authors are doing this with you, they will do it again with others, and they need to be shown that this is absolutely not OK. Please tell the chairs what happened, and identify the paper. I know that's awkward, but you really need to do this.

For anyone reading this who is a student or otherwise writing papers, and maybe hasn't heard this before: NEVER EVER DO THIS.