Yeah, that one seems like a plot hole to me. At first I thought, as is common in movies, there really is no need for the two meetings (fake and real Virginia) to be close together on the same day, other than to drive home the twist for the audience. But then I remembered Adrian does talk to Felix a few times on the phone, confirming that he is with Virginia etc., and I think it does reinforce his belief that everything's going to be fine towards the end. So it is somewhat crucial after all, and it is not really explained. Nor can it be explained by Tomas simply "watching", I don't think.