I have version 1.47 installed...
When did you install the patch? IIRC the crossing the lava too early (before rescuing both imps) bug was fixed with this patch... but if you applied the patch and just played on, it might not have taken effect => you would have to save and reload before proceeding.
Even if you could go back and save the other imp now, you may still have hanging cutscenes and story problems later in the game.... Safest thing to do here is reload an earlier save...
