The little piece of advice that the boy shared seemed to catch House off guard, but he listened and seemed to consider it. His thoughts went back to the mention of the white line in the note and his eyes narrowed in thought. Yes... whoever put them here wasn't stupid. The concept of breaking through, or digging under any white line would have already been thought of.
Whoever was doing this was fond of puzzles. Put in this factor and see what happens. It was something that House was very familiar with. He wouldn't have been surprised if the white line wasn't the escape at all... It was very possibly put there to make the little lab rats THING that it was the door to get out, when really the door was right under them. At least, it was something that Greg would do, if he was in charge. Which he wasn't. His annoyance peaked again.
"I'll remember that." He said it smoothly before he glanced at the boy. "I'm guessing that you tried to cross the line then?"