Does Big Bear Creek stand out to you because it's a large, fast moving body of water in Brooklyn where Mollie could have been hidden and/or carried downstream to a location outside of town?
With 'the world' of possibilities still on the table for why Mollie went missing, 1) is still that she fell/was pushed into the water and carried away, either near the HS or on one of her regular routines, or being dropped off somewhere along the creek, and 2) Travelers on I 80 and Hwy 6 are visually able to see flag displays in Brooklyn, so a passerby on those roads could have stopped in town to check them out, thus a stranger coming into the community and spotting Mollie on a run or walk more of a possibility - this website that talks about Brooklyn's history mentions big flags placed on a rise above town so they could be seen from nearby highways: [partial quote from website]:
"Brooklyn is known as the Community of Flags. In 1991 Brooklyn put up an avenue of flags to welcome RAGBRAI riders into Brooklyn. That gave Alexander Wehrle an idea. He hoped to raise enough money to build a flag display in Brooklyn. One flagpole was to be so tall that motorists could see it from parts of Interstate 80 and Highway 6. He hoped to turn Brooklyn into the Community of Flags.
That idea is now a reality with a large Flag Display sitting up on a hill next to the Brooklyn Museum. '
About Brooklyn | Brooklyn Iowa