lost a bunch of code out of nowhere

Just just finished up coding a 350-line page of code (a bunch of convoluted meticulous 3d garbage) and it was all lost after I switched code pages? It did NOT save the code and I did NOT shut down my PC. I literally have no clue as to what happened. This is upsetting because I sat there coding and fixing errors for about 2–3 hours.

Sometimes "errors" at game running time have this critical effect. So, these situations can be when you testing app, and that app have "errors" ( for example, if you put some "unsupported" files ).

maybe you could try ctrl+z