We rarely see one round penalties but sometimes they are enforced. On a completed board 2♦ 10♦ 3♦ K♦ 9♣, Andrew Doyle was all in sending the action to Huang Jiang Ho. Ho opened his cards revealing 10♥ 10♠ but hadn’t announced his action. Thinking Huang had open-folded, Doyle turned over A♣ 3♣ which Huang saw.
This was then followed with much confusion. Huang insisted he hadn’t acted and Doyle believed Huang’s hand was dead. The TD was called and it was ruled that Huang’s hand was still live because it wasn’t mucked. Huang doubled up but was given a stiff one round penalty.