Hmm... I'll replay the entire game again and check out that scene. I forgot to mention, when it comes to the herb seller, was the key on the ground when you were there? If so you took too long getting there. Once you leave the van for the first time, a timer starts in the background.
After an hour, the sun sets and it gets dark, more enemies spawn and one of the chase enemies spawns far more frequently. This timer doesn't progress while in the van or while in the mansion.
Yeah, there are two codes that unlock in the escape sequence. One for beating it in under 1 minute 15 seconds, the other is finding the secret as I said. The secret is on the mansion map so it's easy to find, once you find it the chase enemy despawns for that map while it plays.