I don't think it was an exotic. It might have been a stock of other material drops to make it look yellow. I'm pretty sure you can't get exotic engrams from a mob in destiny. But I could be wrong.
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I swear to god it was yellow it was in the vault of glass strike it's a joke this game I'm debating to get rid
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it was a green in lighting
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There's no such thing as an exotic engram drop. You did not miss anything.
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Look at it this way, it was probably a SUROS regime! Go buy it from xur! The bugs will be fixed in time.