This feels more like "what's the Unicode character for 'full moon'?" I'd be able to recognize the result as correct, but if I don't know the answer, I just don't know.
(Of course, that goes too far in the other direction. I assume you can draw a few strokes to "get someone started" on a character and they'll pick it up, whereas most people wouldn't recognize the first half of a Unicode code point. As the grandparent poster said, it's an exotic problem that's hard to empathize with in phonetic languages)
In my experience this is not actually the case; I can usually remember a few parts of the character but draw a blank on the rest. You can see the picture of the grocery list that for some characters he got basically half the character right but gave up on the other half (shrimp is the combination of 虫 and 下, you can see he remembered the first half).
I guess there's several levels of character amnesia here, from "I remember half the character" to "I have no clue but I'll recognise it".
That one's just bizarre, since 虾 is also just the most intuitively obvious choice to form a substitute character if you do forget the right component. If anything, I don't think pinyin substitution is something you do unless you're a highly-educated computer user who deals regularly in Latin script. It's a striking "man bites dog" moment, but the one has been passed around since 2006 (cf. https://pinyin.info/readings/defrancis/chinese_writing_refor...) and is not, as far as I can tell, indicative of any particular trend. Discreet literacy outliers in jobs where you'd expect it are ... a thing in English too: https://www.bbc.com/news/stories-43700153
(It's honestly weirder to see someone write jiu菜 than 9菜 too.)
This, it's honestly not helpful to pretend it's the same as misspelling a word in a phonetic language because it's not and it's not even a good analogy to begin to understand the issue.
I do not know if this is true in all the German dialects, but at least some pronounce "wider" with short "i" and "wieder with long "i", so they are easy to distinguish when heard (like the difference in English between "fill" and "feel").
English and German appear to have had a similar semantic evolution for this pair of words, because "wider" means "against", while "wieder" means "again", so in both cases a single word has evolved to cover these two different meanings and the variants have become differentiated in pronunciation too.
"ie" is always long. For "i" it depends on the splitting of the word, i think. I don't know if this is a concept in other languages too. I think the rule is that if the "i" is at a split, then it is long, but i'm not sure and there are always exceptions to every rule in German. Consider "Schnit|zel", "Lis|te" (short) vs "Bi|bel", "Wi|der|stand" (long).
From what you say I assume that the literary pronunciation is also with long "i", which is good to know.
Perhaps they were influenced by the different spelling, because I have seen this phenomenon in other countries, where despite a mostly phonetic writing some words were spelled differently than pronounced, for etymological or other reasons, and then the pronunciation of those words by many people has shifted, matching the spelling and not the traditional pronunciation.