I'm on watch and wait, so I haven't had any surgery that could cause memory problems. I've noticed problems with word retrieval too, and with my working memory. I'll have four or five tasks in mind that I have to do or a sequence that has to be completed, but as I get into the first task, the rest slip out of my memory. I've never forgotten something that I've *done* - my long-term memory seems fine. I just forget what I have to do. Needless to say, I have lists all over the place, and when I have to rely on my memory, I internally repeat my list many times until it sticks.
I can't say whether this is related to my AN, or the stress related to my AN. I experienced similar memory problems with both my pregnancies and when my children were infants, when sleep-deprivation and hormones can cause memory problems. I'm perimenopausal right now and memory problems are a known symptom of the hormone fluctuations of perimenopause.
I also experience memory problems when my allergies are acting up, or I have a cold. Congestion in the head can cause these same problems. There's been some recent research that shows that having a headcold impairs your memory and reaction times just as much as having the equivalent of one alcoholic beverage per hour does.
Regardless of what's *causing* the memory problems, it can feel debilitating and I really empathize with you Mei Mei. Are you having problems with word retrieval only when you write, or also when you speak to people? I do it more when speaking - when writing I have enough time to think about it, or can type ahead and go back and fill in the missing word later, when it springs to mind.