Good morning.
As you'll understand, it is your own responsibility to take care of your own license key. Vstep may decide to help you, but of course they're under no obligation to do so.
To ask them for help, you will need a proof of purchase, such as the original receipt from the shop from where you purchased the game, or something else equally convincing.
You can do this via the "Contact us" link on the left-hand side of the front page of this site at
www.shipsim.com
As a general precaution, always write down serial numbers/license keys etc and keep them safely stored away.
In the case of Ship Simualtor, you can of course store the keys in your profile here.