You stand around and let time pass. You take this time to look around the SmallStore a bit more.
There is a clock on the wall that states the time as 7 o'clock. This doesn't help you figure out what time it is much better.
There is a MetalDoor in the back of the store, near the drinks refrigerator, and AnotherDoor beside the counter, on the other side of the store from the office from the entrance.
It's been a few minutes, and there's still no sign of the clerk. You could always try to CallForHelp, or go back out to the LeftAlley.