4.05 - Run

Chloe and Clark stop by the Talon to get coffee and talk about where he might go to college (we already know that Chloe is going back to her home town of Metropolis togo to Met U in thefall.). Clark talks about going to Miami (he checked it out in Run with Bart, and it's a set up for Aqua.) While they are there, her cousin on duty is robbed and doesn't remember it. Clark rushes outside to confront the robber who zaps Clark - erasing all his memories (and we see a still from every episode in the series thus far.) Chloe comes running out of the Talon to check on him, and Clark looks up at her confused. "Clark who?"

Smallville, Episode 4.05: Chloe, Clark, and Bart

Clark ends up tracking down Bart, a kid with a handful of other Flash alias, whom stole his father's wallet.  Clark talks to Chloe and has her track down Jonathan's credit card, and with her help he finds out that the kid used it to buy a hotel room.