Pretty sure the biggest victims of this were Rockapella (who apparently did every a cappella song) and Weird Al (who apparently recorded every comedy song).
Here’s how cool Al Yankovic is though: for years he maintained a list on his website of every comedy song falsely attributed to him and all the actual artists who made them. I don’t think it’s up anymore, there can’t be much need for it these days, but Al was very cool for doing that.
Yes. I once downloaded a Stroke9 greatest hits album, and it included the song "Story of a girl". When it came on, I thought "huh, I didn't know they did this song. Cool." Then for more than 10 years I thought it was their song.
Don't Worry Be Happy by Bob Marley was the one I remember. It was not by Bob Marley at all. It was by Bobby McFarren and came out years after Marley died.