It's possible to repeat the question, "You did play tennis yesterday? Did you?" But that's not a tag question. I'd call that answer very unfair. It's a good example of why I don't like joining sentences with commas. Many people would accept "You did play tennis yesterday, did you?" for what I just wrote. Of course the intonation and the context are completely different with these sentences from one with "didn't you?" (in speech).
Anyhow, you say "you were told" the answer was "did you". Who told you?
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