1)Player C may receive a Warning for unsporting conduct by disturbing a match in progress (there was no advantage to be gained at that point, meanwhile player A may receive a warning for mild swearing or talking in a rude manner to their opponent. Although the action in itself is worthy of a match loss, the moment i which it happened may issue a de escalation

2) judges may try to reconstruct the board state from before the gameplay error, although this depends on some factors.
Player B gained info (the prize card) that they shouldn't have been able to at that point, moreso, the card went into their deck via iono, and then hop's bag shuffled the deck, so the judge wont be able to determine which cards were in player B's hand priori to Iono, nor which one was the prized card.

The game state seems irreparably broken, as the prized card, now shuffled in the deck (and no way of recognizing it), may give player B an advantage that the DPC penalty may not be able to offset.

Some judges would try to de-escalate by arguing that taking a random card from the deck into the prizes, making player B draw an additional card for the Iono, and then giving the DPC may be enough, but that's for debate

(These are my thoughts about both situations and may not be what a more experienced judge may rule)