When editing some elements on the canvas, if you move the mouse by mistake, the ruler and canvas will also move. Just as the picture shows

The question is, where is the canvas, and how to find it quickly?

On the lower-right corner of the software, you can find the canvas scale indicator. By left-clicking on it, you can easily return the canvas to the center. 

Additionally, when you hover your mouse over the canvas, a zoom ratio list will appear automatically. This feature allows you to choose the desired zoom level quickly and easily.

Enjoy your laser time!