Yes, I do remember.
Kim went back to look for Crystal's "things", which may have, in her mind, included the shoe, or maybe not. Maybe Crystal DID find her shoe and forgot because she didn't put it on, or one of the boys found it while the women were finally leaving after Crystal fell or lay down on the steps, and it wound up getting put somewhere in Kim's car. If so, Kim probably threw it away when she came upon it, perhaps the next day. It's hard to say what became of the shoe, but we know the cops didn't find it at the house.