"Hahahaha! It is so amusing to know that even now Humans have been nothing but idiots! All I needed was some money and the humans that arranged for his trip all shared the info. I didn't even need to drink any blood."
I see. Certainly, it was true. While David's entourage would have surely talked to the upper management of his journey, it was literally impossible to keep the lips of everyone sealed.
This was the primary reason that soldiers were had to get permission for leaves. The closer the major operations became, the more soldiers got tense. While higher quality people knew how to deal with the pressure the weak minded could not.
Alcohol and women were the greatest weak points in this regard. All to often a slip of the tongue was all it took to deduce a scenario in the minds of a master strategist. Many of the anime I watched showed how powerful and how deadly it was to leave soldiers with loose lips or bad drinking habits.
