This happened to me just yesterday! I was helping a co-worker with a problem, and I noticed some redundant code in the same function, so I told him he could simplify it while he was there. His response was, "...but you wrote that". (And as it turns out, only a few days prior!)
In fact, I often conciously refrain from using blame on an "interesting" piece of code because it doesn't matter who wrote it. Looking it up would just satisfy idle curiosity, but yield noninsight into how to improve the code. In fact, I think that blame should just list the commits, but hide the authors by default. "What changed? " and "how?" are always much more pressing questions than "who?".
Pinning bad work on a person does not make progress. Fixing bad code does.