You are nicer than I am. I would have tossed the cards in the garbage and then stated what you found and what actions you took. In fact, in my sitch I found artifacts of the A she was having and destroyed them and did not tell her. A few of them had monetary value. Boundary stated with no words.
I did consider that bdub, but yes I'm too nice for my own good. Plus, I have to be vigilant for passive aggressive reactions and this may well have constituted one.
M: 57 / EW: 52 T: 21, M: 8 S: 18, S: 15 Bomb: 1 Jun 14 EA Aug 2014 I think PA Feb 2015 possibly sooner