i understand the responses however i too recall "free tap water!!!" (said like oprah) being an option to BoB when the announcement was made.
i also agree with the fact that it is indeed reliant on memory so it is understandable why crew would not recall after serving another 100 people after the OP--but really. this is plane tank tap water (which i would never drink) and if the OP wants it--he should get it!
side note--i cant believe thats true about IB! never flown them so didn't realize they could be WORSE than BA :P