I don't remember having a missing render on my playthrough, but I checked the folder and that render is missing for me too. 11&13 are both there, but not 12. So it seems like a common issue.
Yeah that is not the only scene that is missing either. ch2_scene10_8 is also missing. So far that is all I have seen.
Simply editing "script_2.rpy" with notepad++
Change line 2352 from ch2_scene7_12 to ch2_scene7_11
Change line 2579 from ch2_scene10_8 to ch2_scene10_7
Change line 2992 from scene ch2_scene10_b_63_ to scene ch2_scene10_b_63_anim
Change line 3013 from scene ch2_scene10_b_70_ to scene ch2_scene10_b_70_anim
And everything works and seems flawless in the transitions.
EDIT: You know what here use this edited versions so that it fixes all the image and grammar mistakes.
I will give the scrappy mod version to Scrappy so that he can get his version fixed as well.