What's a parent to do?.....

3- year old Abby stole in to big brother Lucas' bedroom commandeering a Lego car. Oh how sweet to play with forbidden goods, until.... big brother found her. He nicely requested she return the pieces ( by then she'd disassembled it) of it to him.  Refusing she popped a piece into her mouth.
"Momma! Abby has my Lego piece and won't give it back and I asked her nicely!" he whined at me. I followed him to her bedroom where he was attempting to make a forceful entry. Pushing him aside I went in to talk to her. "Where's the lego piece? " I asked. "In here!" she replied pointing at her mouth. "You got to be kidding me!" I thought. I tried rewording it. "Abby where did you leave brother's Lego piece?" Opening her mouth wide she said, "In here!" Oh boy! What's a parent to do...