Apologies if this has been discussed in the past but Diana's case is similar to Angela Hammond's. They resembled each other, they were close in age, they disappeared within a 5 year time span of one another, and both were abducted from parking lots late at night. Festus, MO is only four hours from Clinton, MO- not terribly far if the suspect was operating in Missouri during those years. It could have easily been an opportunist trolling in smaller towns off the highway.
In contrast, assuming eye witness accounts of Diana's case and Angela's description to her boyfriend were accurate, the possible suspects from each case look nothing alike.