This happened; I was a university professor for many years, I wrote lots and lots of letters of recommendation for people to get jobs or to go into graduate school. And probably about 95 percent of them, I have no idea what happened.
Me pasó a mí cuando fui profesora universitaria mucho tiempo. Escribí innumerables cartas de recomendación para alumnos que buscaban empleo o para ingresar a la universidad, y nunca supe qué pasó con el 95 %.