Sometimes...
...when former WLs fall off the radar, it's because they WANT to do so. Hankering for contact details and seeking the one perfect code that will result in them seeing you again will only lead to disappointment. If they want to re-emerge, they will. If they don't, no amount of questions will change the situation.
Please feel Reviewee to apply this to Louisa, Cherry, Aimee etc. etc.