Except in the cases where: someone tries to port the code to another language, or they decide to use a different formula / algorithm; and they notice the result

Except in the cases where: someone tries to port the code to another language, or they decide to use a different formula / algorithm; and they notice the result. In the real world, most scientists will keep modifying their program until it gets an expected result (either because the program is correct, or because multiple mistakes cancel each-other out, or the standard theory is wrong but they feel obliged to keep debugging until they can prove it to be correct). Sure, there's times when a computational model proves something interesting (unexpected), but then the researchers may have to open source it just to prove they didn't screw it up.