Could he have stored drugs again and asked for another dinner together?
Would he have had enough time to try this?
It obviously sucked for him that she knocked the drugged wine glass over.
But now that he could move around the house when she was gone, couldn't he have went and stolen more drugs again (not too many to avoid suspicion) along with storing the ones she was giving him? Then wait a little while for another "groundbreaking" development in his story and ask her if she would do the honor of having dinner again to celebrate the occasion.
Then, do the same thing he tried the first time, making sure he asks her to leave the room again to get something. Just make sure it's not a candle. lol