Seto had sat at the table next to Mokuba when he started eating. When Dartz asked where the three were, Seto was the one to chime in. "Cora went to let them know breakfast was ready. She may have remembered Adam is here too." Having noticed that Adam wasn't with them here eating. 

Kuriboh hurried back and started flailing and cooing hurriedly like he was explaining what was going on. Cora's eyes widened like she understood what Kuriboh was saying. "We gotta get him out! Maybe if all three of us push the door we can get it open." Cora suggests.