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.
Because shrimp meat is something I see written out EVERYWHERE.
It just seems like such an odd outlier example. Like talking about a friend that spells "been" as "bin." I'm sure it could happen, but it's not indicative of a broader trend.
The story was reported by Victor Mair, though, who is extremely opposed to using characters and often exaggerates the issues with them.
Personally, I've seen a lot of Chinese people's written notes, and I don't think I've ever seen them resort to pinyin, even among people that didn't go to college. I just asked a few Chinese friends about this, and they told me they never resort to pinyin either.