A note - manweb's instructions will only work if you bought your version prior to the launch of Simulator Central. If you bought it after that, you will need to login to your account on that site and look under Order History.
Not applicable for the OP, but just going to post this here in case someone has the same question, actually uses search, but indeed got the game via simulator central.
For those people, you can re-download your game via this link: https://www.simulatorcentral.com/index.php/downloadable/customer/products/limit/50/
Or: Log into simulatorcentral, go to "My account" at the top of the screen and then select "My downloads on the left".