Muck help

I cant find my way off of mucky island. the cave where im supposed to find remains of some old womans son turn up dry every time i go back through it, there are two locked doors i cant get through that cast spells if i try to pick them, ive walked over every spec of the cave and i havent been able to locate those damn remains. Ive even tried striking every wall in the place with weapons but still nothing. Also i noticed that i was given supplies that had food, will this food go bad after a set period of time?