Did you see a MD5 collision that happened randomly, or was someone intentionally trying to create one?
Intentionally creating a collision with MD5 is fairly easy; having one happen at random would require creating something like 10 ^ 14 billion hashes in order to have the same chance of a collision as winning the lottery. People win the lottery, yes, but they don't happen across MD5 collisions by accident.
Random! I don't remember the details, but we spent a good half hour looking up probabilities and marvelling at it. I think at the time nobody realized just how unlikely it was, should have saved the inputs :(
Intentionally creating a collision with MD5 is fairly easy; having one happen at random would require creating something like 10 ^ 14 billion hashes in order to have the same chance of a collision as winning the lottery. People win the lottery, yes, but they don't happen across MD5 collisions by accident.