When an adult goes missing and is then found dead, although there are endless scenarios and possibilities, in general there are only a few causes:
1. Voluntarily Missing (Runaway): With Cheryl's body being found it is clear she didn't 'run off to Mexico' to start a new life. This theory/cause can't be true.
2. Suicide: Obviously sleuths on this thread are divided as to whether she did or did not commit suicide. I'd love to know how many people felt she committed suicide before they read about the 'self inflicted cuts'. The wording of that statement makes it sound as if Cheryl had been in the habit of harming herself or had harmed herself on that morning. Although that wording tweaked the idea of suicide in my mind, I really think it was meant to imply that the cuts were superficial, and caused by normal activities (such as an accident with knife or scissors) as compared to defensive wounds or injuries caused by an attacker. It is strange that the information about the cuts would even be released to the public, if it is in fact unrelated to the case. Perhaps those were the only marks/injuries on her body. With the family reporting no history of mental illness or drug/alcohol abuse, and Cheryl texting that she would 'probably ride home with her carpool (future plans) it seems unlikely (but not impossible) that she committed suicide. Dead bodies can't hide themselves. So if she did kill herself she would have had to do so in the culvert or in a place where she could fall/roll/stumble into the culvert. Toxicology results may help here.
3. Accident: Sometimes people fall off cliffs or get drunk and drown in lakes. When their body is found it might be unclear at first if it is an accident, suicide, or homicide. Based on where Cheryl was found in relation to her car I can't think of any plausible scenario that would account for an accidental death involving no foul play. If she was struck by a vehicle walking to the bus someone might have scooped up her body and disposed of it--but autopsy would have revealed more injuries and possibly forensic evidence at the scene of the accident. And that would not explain blood in her vehicle. It think there is no, or very low, possibility she died accidentally.
4. Abduction/Murder: MSM makes it seem as though there is evidence of Cheryl being alive and well on her way to work around 7:00am. Although it never explicitly says that Cheryl can be seen on video, or seen driving her car, the implication is there. The implication is also there that Cheryl sent the text about forgetting her badge--although some will debate. Since Cheryl didn't make it home to get her badge, and didn't make it to work that day, the most likely scenario is that she was abducted and murdered shortly after sending the text (her phone was reportedly powered down shortly after the message). I wonder if the autopsy has pinpointed a time of death (did she die soon after the text or many days later), and how long she was in the culvert (dumped on the first day or closer to the day she was found)? I think there is a high probability she was abducted and murdered, but why (motive) and who (random stranger versus friend/acquaintance/coworker/neighbour)?