I'm not sure that the bodies were left in the open or easily discoverable, but maybe the answer as to why the bodies were left there has to do with the manner in which the perpetrator arrived and exited the area. I note that the ISP previously stated the following:
“We are asking people that were driving through the Hoosier heartland that might have seen a hitchhiker or saw somebody walking. We are asking people in Logansport all the way to Lafayette if they saw somebody around that late afternoon on February 13 walking down the roadway. We would like to know about that person,” said Indiana State Police Sgt. Kim Riley.
That suggests LE believes he did not arrive at the scene via vehicle. Thus, the possibilities that he entered/exited the area on foot (which suggests he may live in close proximity) or that he used some other means to arrive/exit, such as a canoe/kayak. I'm not sure what the water levels are at this time of year are in the creek, but leaving the bodies within 50 yards of the water would support this hypothesis. We also know that there was a search of the river and it is standard practice for LE to not only search the crime scene but routes of ingress/egress. Lastly, if the perpetrator crossed the river, being wet and on foot or a vehicle would attract attention. Being wet in a boat would not necessarily attract suspicion.
Food for thought, but as we have limited information about the crime scene it is rank speculation.