After going cross-eyed yesterday, wading through new members to see if I could figure out who the witness is, it turns out that all I had to do was look in the "edit history" for the post. (Click on the three dots in upper right corner of post, choose edit history). In his first version, he gives her first name! Only two people by that name joined this year, one in June and one the end of August, both Americans.
I don't see any reference to a trip to Mexico on either one's FB, although that could be due to settings. Both "look" reputable. JR indicates in his post that Jenny is in Mexico because he specifically asked for help from members in Mexico. I'm not sure what to think except how could anyone could remember an encounter with a random Asian woman in Mexico after eight months?...unless Jenny made quite an impression. But how did this witness track down the HFJ page? Did Jenny give her name? Anything is possible and I certainly hope she is alive. Naturally, we can't sleuth or post anything about this person here.
https://www.facebook.com/groups/helpfindjenny/permalink/883905658451146/