Multisteps Webform loses current page when refreshing browser
For this purpose I use Multi-step forms module. This does all the heavy lifting for you. It allows you to use a session storage so if the page gets refreshed or the browser gets closed, it saves the current step.
Multi-step forms:

Mforms module is a set of tools that help to create advanced multistep forms in Drupal. It can be modified and extended so a developer has full control of the way how individual form steps will be handeled, how and where will data be between form steps stored, which step will follow, how form controls will act and how the output will be displayed.
The main differences from existing multistep solutions for Drupal are robustness, flexibility and extensibility. You can even dynamically change the steps sequence and jump from one step to another regardless of their order.
Read documentation.