She'd actually noticed the van missing first, since she came in through the garage to drop off a few things that she'd taken with her. She was puzzled, mostly due to the hour, but not overly concerned.
And then she found the present, and that just got her all sorts of curious. So, after making sure that there was someone to watch Henri for the night, as there generally was, she tucked the box with the darts into one of the pockets on her Bag of Holding and slipped into the Backstage, heading for the address.
She'd gotten good at pinpoint location through the Backstage since she'd been in Bizarro-World, and it wasn't long before she was just there, sitting across from him, elbows on the tabletop, chin in her hands.