You might learn they’ve died and it will totally ruin your night.
I am distraught having just learned that my absolute favorite teacher from high school, Richard Marc Tiffen, passed away after a 15 month fight with brain cancer 3 years ago at the age of 51. He wasn’t especially popular among my friends for some reason but we got along really well. I had him for science and photography for several years and even graded tests for him, just to be able to spend time with him. I just thought he was the most awesome guy, let alone teacher, and I guess that was reflected in how I related to him because his assistant teacher once remarked to me, “you treat us like people, not teachers.” At a school where I often felt out of place and miserable, he was one of the bright spots in my day. I once did something stupid and he called me on it and I felt really crappy about it for years because I knew I had let him down, even if it was in a small way.
I hadn’t corresponded with him since college but you assume people you knew in the past are living their lives and that you can pop in from time to time. I think I had told him how much of an impact he had on me but I wish I could have connected with him as an adult to tell him again.