I was a licensed vendor at Penn National Racetrack for many years and can give you some background about the track and the atmosphere there.
Penn National has come under much scrutiny in the past few years due to owners who were pushing the limits of the rules and trainers who were drugging horses. There had been an ongoing grand jury investigation for years looking into matters there. I don't know of any other track in the North East that has been watched as much as Penn National. I know many people who will not go on the backside there alone, although I will say I did for years and never had an issue.
In order to get on the backside of ANY racetrack, you must be fingerprinted and have a criminal background check. Once you are checked out in one state and licensed, that information can be shared with other states to make licensing easy in the other state. At one point I did have a delivery driver who could not deliver to the track as he could not get licensed because he had a previous conviction (though I cannot remember for what at the moment). I was licensed in PA and DE and have been on almost every track in PA. You have to check in coming through the gate every time you come in. At Delaware Park, the guards were a little more lax; at Penn National they asked for my pass every time I went in. Records are kept of all coming onto the backside. You could bring a "guest" with you but if it were done on a regular basis the guards would eventually not allow the guest on and tell them to go get a license.
The track environment is not a pleasant one in my experience. Although I am not a fan of what happens to the horses there, what happens to the people is just as bad if not worse. Many live in little concrete block buildings on the backside that are just tiny rooms with a shared bathroom between a bunch of them. They eat in the backside cafeteria where the food is a step above deplorable. There is not much to do and I do not think the workers make much money. I think life in general is a struggle on the backside and that is not being dramatic. I have seen posters advertising 12 step meetings for both alcohol and drugs and many religious groups have outreach programs specifically geared to backside workers.
If there was a trainer who had committed seven murders, someone would have had to notice and it could not remain secret. To commit seven murders either puts you into serial killer territory or Mafia hit man status.
Most trainers at Penn National have a barn or part of a barn there and may have an off track farm as well. Many have a home base and may travel to another track like Charlestown or one of the upstate New York tracks. A few will haul to Florida for the winter and some have other operations that they work between. BUT, for the most part, it is a fairly consistent lifestyle and if seven people, all with one common connection, came up missing, someone would have to notice. I have no doubt that drugs flow through there but am not sure how huge of an issue it is compared to any place else at this point.
What I witnessed on the backside was not highly cerebral criminals, but more people trying just to get through life. It is seedy and sorted and sad. And, let's not forget, drugs have a way of dumbing people down.
The impression I got of the overnight guest and his buddy are a couple of things. 1) They are probably not as tough as they'd like people to think. 2) They are certainly not as smart as they'd like to think. 3) They like to party. 4) They seem to make the same mistakes time and time again and not learn their lesson. 5) I can see them telling stories to establish reputations but those stories not necessarily being true.
I can also see someone feeding Amanda information to see where it goes and what she repeats. And I can see her being not quite smart enough to NOT repeat it. Again and again and again!