Oops, actually, apparently I didn't pass it. X_X
I thought I did because the lemming is actually doing the exiting animation and I hear the "boink" sound.
But apparently, after I've posted the message and switch back to the DOSBox window, the screen says 0% rescued. Arrgh!
This sucks, but being so incredibly close, I'll try again and see, since I didn't assign the floater at exactly the last possible moment. (I must say, the SuperLemming thing gets very annoying after a while.)