It's possible to miss a couple globules of biofuel since there are so many of them, and they can also spawn inside walls (which wouldn't make them impossible to pick up, but would make them impossible to see). I forgot to fix this by changing the drop to a single large pickup before release, which I'm going to do now!
I've been thinking about adding a task system or a map of some kind, I'm not sure exactly what form it would take but it's a good idea.