I blew it. After deciding to rethink and revisit DMing under a general sense of what OSR means, I went back to old habits.
I fudged a dice roll to avoid character death.
I knew I made a mistake as soon as I had done it; however, I didn't feel like it would be kosher to go back on it, to suddenly say "actually, the ghoul's second claw rake carries most of your ribcage with it" and retcon the death of Guy La Rouge, Level 1 halfling thief.
The background: it was a one-shot adventure that turned into a two-shot while half of our usual group were out of town. I decided to try playing Basic Fantasy Roleplaying and quickly wrote up an adventure involving an angsty 15-year-old possessed by a dead necromancer terrorizing his stultifying rural community (it must really blow to be in a dead-end town known for honey production when you've got an 18 for Intelligence (rolled legitimately!)).
Showing a surprising ability to compensate for their low HPs (the fighter-mage has all of 1), the party negotiated various encounters and managed to track the angry teen who doubtless would have been really into Wumpscut in a more modern setting and engaged him in a climactic battle where he called forth the spirits of the evil cave where he had decided to tack up his Revolting Cocks posters.
The ghouls were actually pretty ineffective, managing only to paralyze the dwarven fight Brunt "Cozy" Ditka, so I may have also fudged an extra ghoul (showing up late, he probably went to check to see if the oven was still on) who then of course rolled incredibly well, leading to the death fudge. My just desserts.
The main question is, how do I avoid this situation in the future?
The only answer that I've come up with, and I think it's really the only solution in this case, is to roll in front of the players, to enforce non-fudging completely. I'll give it a shot in the next session and see how it goes.