It's not just a SINGLE flip-flop that makes this a LOGICAL place to search.
It's highly unlikely they can prove the owner of a single flip-flop because the mate probably is long gone.
It's the TOTALITY of the reasons CocoaMom even zeroed in on this area..... starting with the PINGS.
If LE picked out a couple of areas to search ONLY because of the pings & little more, then I think they NEED to take a look at the reasoning here.
Pings, water, woods, playground, ease of moving around without being questioned, parking lot, potential buildings (shed?) to leave a drugged child while you party.... OR a place she's been where she knows she can dump a body.
We KNOW Casey had a lot of hours to kill waiting for her friends to get home from school or their jobs.... it's likely she'd not be anxious to be caught walking around with Caylee when she's supposed to be at HER job & her daughter is supposedly with some make-believe nanny.... she'd afraid she might run into someone who might tell her family they saw the two girls.... Casey would want a 'safe' place where they can wait until it's safe to go back to the house.