I killed Mom's Heart recently but instead of jumping into the chest, I went through the Devil Room into Sheol. After killing Mom's Heart a few more times in different runs I've noticed that 'End 1' is blocked out in the 'Stats' menu (but not End 2 / End 3 etc.). Is this a glitch / is there any way to force the ending?
It's most likely a bug.
My best guess is that the devs didn't expect someone to actually skip the big yellow chest and just didn't build any safeguard in for that.
The only thing to do would be to mail (for support):
- Or go to the Binding of Isaac Reddit and make a post there.
Make sure to also give them a screenshot of your problem and hopefully they will patch it.
Alternatively.. You'll have to start over again.