The My Hamster section can be expanded into multiple Maze spaces. You’ll want to open the My Hamster inventory interface to make sure you’re not on a second or third Maze.
If you would like to see the hamsters in another Maze (Maze 1, 2, 3, or 4), open the Hamster menu by selecting the tab in the upper-right corner of the My Hamster area. Once you have that menu open, click the My Mazes button.