This situation came up in a match today:
First, I landed Welsie's Grand Tapestry finisher which emptied my opponent's hand.
On Hit: The opponent is stunned. All cards in the opponent's hand are discarded together with their attack pair this beat.
Then, when their almost-entire hand was in their discard pile 2, I landed Anomalous grasp. This moved their discard pile 2 back into their discard pile 1.
On Hit: Place your opponent's Discard Pile 2 into his Discard Pile 1.
Since Welsie can keep playing the same attack over and over with her UA as long as it hits, I was able to keep playing Anomalous, which eventually led to my opponent having no hand and no Discard Pile 2. We ruled that this meant I got to keep playing attack pairs without them doing anything. After a few more very one-sided beats, I won the match.
Did we play this correctly? I've never had a situation before where someone had no cards in hand at the start of their turn.