About ten days into her cycle, my girlfriend and I were messing around in the back seat of my car. She was sitting on my lap and we were grinding around. I had on cotton boxers and she had on a thong that only partially covered her vagina. There was no penetration. When we were finished, we noticed a small quarter sized stain near the top of my boxers. This stain could only have been pre ejaculate because I had no orgasm and did not ejaculate in any way. I had not ejaculated in a week prior to this night and had urinated multiple times since that ejaculation. She changed underwear and took a shower about an hour later. We were still worried, so the next day (about 14 hours later) she took the first Plan B pill, and followed with the second 12 hours later as prescribed. What are the chances that she could have become pregnant from these occurences?