I had a really useful, illustrated book on sign language when I had a student with a severe hearing problem - another one of my students had a deaf/dumb auntie, so was fluent, and her father kindly, hearing I'd been trying really hard - I often communicated almost exclusively via swift but accurate drawings, fortunately a skill I've always had - sent the book in for me, and I kept it to hand in my desk drawer.
Unfortunately, when I retired, speaking to someone I'd worked with, who was still there, who was having a similar problem, I suggested she look and see if it was still there.
My replacement had binned it, along with dictionaries, thesaurus, copies of the Bible, and Koran, the Jehovah's witness Bible, and other reference works!! Straight away. She said they were all no use!!
(I used to find the Religious books very useful when a student said that their Holy Book would not allow them to do something - hand it to them, and ask them to find the reference. They never could. [ I'd, by the way, read all the Holy Books, so usually could sort it out. Other Half said I'd read anything, even the label on a sauce bottle - he was right] It always pays to know what you're talking about.)
Really wish I'd gained MAKATON skills.
TY