It's not on the bloaters body.
If you restart the entire checkpoint, try to find the little key card first. It's on the 2nd floor in a room where there's a bunch of little TVs/monitors.
Grab that, go and start and generator, and try to run to the door down the hallway as quick as you can. Try to run around the infected without fighting them since you're low on ammo and other weapons/crafted gear.
Yup, that's exactly what you should do.
Don't waste your molotov, you may need it for later and there's truly no point in using it on the infected in that room when all you have to do is get that key card, start the generator and get the F out of there as quick as possible.
I'm going to tell you now though, after you get past that part - make sure to conserve your ammo and gear as much as possible because you'll definitely need it later in the game.
Try to approach certain situations and be a little more stealthy, take guys out quietly, and hope to pick up ammo. Make sure to check every room you come across to find some that you can use to craft molotovs, nail bombs, etc.
You may want a melee weapon as well, of course. I'm saying though, try to do things a little more quietly and you will definitely have enough ammo/gear for other parts in the game when you really need it.
Oh, and to save ammo, just beat people over the head with a brick or something lol, seems to work pretty well for me. I'm playing on the hardest difficulty, so I NEED to conserve as much stuff as possible.
Just a few little tips. I've already beaten the game like 4 times, but it's so addictive and such a great story.