Just a few thoughts on the search for YY. Some of my info is just MOO, some from news reports, some from court testimony, some from my knowledge of LE in Champaign County, some from my intinate knowledge of growing up and working on farms and having many farm friends in Champaign CO.
1. The FBI has only a few agents permanently assigned in the Champaign office. Their job in a missing person case is to liason with the much more numerous local LE agencies in the area for the search. The FBI did call in other agents from Springfield and Chicago but these agents were mostly tech experts and crime scene investigators.
2. From local news reports, from the 55 minute interview with BC around June 15, it was clear that LE was working extreme hours looking for YY. There were many tips reported that had to be followed up on, both the FBI agent and the UIPD officer said they (and I assume many others) were working till midnight on the search for those first 6 days.
3. The LE and citizen search efforts were not heavily reported by media and I don't know why. But the agencies involved included: FBI, UIPD, Urbana PD, Champaign PD, Champaign Sheriff Dept, Champaign County Search and Rescue with trained search dogs, LE dive teams, at least 600 U of I Chinese students, and unknown contributions from smaller PDs in Champaign CO. Many hundreds of hours of overtime were put in by these hundreds of LE officers searching for YY.
4. The remoteness of areas in Champaign CO has been quoted in this forum as "vast" to "most farmers know what goes on near their farms". Fom my experience as a high school student and U of I college student in the 80s, if we wanted to drive out to a remote cornfield using a dirt access road between or next to the field we could drive in 50 yards off the county road and be hidden by all cars passing by (if any, which weren't many, and sometimes none) and drink beer and play music all night if we wanted and nobody ever bothered us. We never left a mess so no one knew we were ever there.
5. There are literally thousands of remote turnouts in fields within 20-30 miles of CU in any direction: N,S,E,W. It wouldn't even take any "scouting" to locate a remote place like this, they are everywhere. And unlike this year with the wet fields, the corn crop was already fairly high in June 2017 as seen in the photo of YY out at a U of I field testing location.
6. It would only take approximately two hours max to drive from CU to one of the remote locations in the nearly completely unpopulated areas 20-30 miles from CU, bury a body Ted Bundy style, and be back home in CU. His vehicle had no GPS tracking system like OnStar, he left his disabled phone at home, disposed of YYs disabled phone and backpack no telling where unless he buried them too.
7. That would use around a quarter tank of gas which would leave another quarter tank to drive around campus looking for other victims prior to YY plus run errands to buy rum and cleaning supplies. You can pretty much drive every street in and around the U of I campus in a 30mpg Astra on a quarter tank of gas. The campus isn't that big area wise.
These are MOO based on my experience driving 75% of the country roads in Champaign County over the years. (I worked as a surveyor and in road construction in Champaign County for several years in addition to growing up in the country in the County).