The fact that 嚔/sneeze is usually the go to example means it ends up becoming the exception that proves the rule. Most other characters are much more easily remembered.
If you learn languages you quickly notice that knowing the 99% most frequent words still means that you need to look up a word every paragraph or two and that you have trouble expressing yourself. To write Chinese you need to know several thousand characters, forgetting just a few dozen can be quite annoying when you try to write nontrivial texts.
Being able to write a character by hand, being able to type it up, and being able to read it are all different things. I doubt many Chinese would be thrown off from reading or typing 打喷嚏.
I actually did a deep dive into the issue of unfamiliar characters coming up when reading, and how people handle them. I won't go into all the details, but the general takeaway is:
1. Unfamiliar characters can actually be quite rare or quite common depending on the material you're reading.
2. It's not much of an issue for people either way.