I'm not sure exactly how far the reception area is from where Jim is standing in the warehouse, but roll Listen for him. If he succeeds, then he overhears it.
Cryptography is for making and breaking complex codes. All you really need is simple signal that both Lewis and Malone understand, which doesn't require a roll. However, as long as Lereux is in the room, he won't be able to communicate it to Malone so that she understands it and he doesn't. Don't worry, though, he won't be in there forever. The arrival of the truck may get his attention once he hears about it.
Cryptography is for making and breaking complex codes. All you really need is simple signal that both Lewis and Malone understand, which doesn't require a roll. However, as long as Lereux is in the room, he won't be able to communicate it to Malone so that she understands it and he doesn't. Don't worry, though, he won't be in there forever. The arrival of the truck may get his attention once he hears about it.