Have to admit that I sometime simply forget to put my new BAEC card into my wallet. So yes, I am one of those persons who sometimes have to rely on getting in a oneworld lounge on the basis of boarding pass / graceousness of lounge staff alone. Usually works (in TXL, I never actually need the card, as then lounge staff & myself are on first name basis ).

In T5, have been the occasional witness to DYKWIA's trying to get into the lounge - unsucessfully in most cases, might I add. In TXL / STR, have never seen that happening - maybe because the BA lounges are hidden.