"Why didn't you warn me there was a trap there!?"
"Hey Imoen, you haven't seen that gold necklace we picked up, have you? I was just wondering because I found out it was cursed."
*laughs!*
How about:
"Say, Imoen. You know all the stories they tell about what happens to thieves who steal from archmages? You have a unique perspective -- what do you think? And who would you sooner wager on, the thief or the archmage?"
"Remember the night... the night we left Candlekeep? I'm so glad you followed at a distance instead of hiding in the luggage-- had you done that instead, you'd have died as well... but what made you do that?"