So, when the captain drops the PCs off at the Isle Of Terror the book says he only waits 10 days, after which if the PCs haven't returned he assumes they died and goes home. Has anyone had the PCs actually take more than 10 days (but not die)? And how did the PCs get back home? I was thinking if they can cast sending they could just send one telling the captain "Hey, we're still alive, come back".
I ran this a while back. The PCs usually return in time as the whole point of having the captain state that he will only wait ten days is to keep the PCs focused and on the countdown clock. The countdown ramps up as the city's golden trap erupts, so the players door really play around too much.
If your PCs miss the boat, literally, you could have a merchant or fishing vessel from Nirmathas, Razmiran, or Kyonin show up off shore.
Alternatively, you can just let them work it out on their own.
Also, look into Jalenara, the nightshade, in Undead Unleashed as it makes for a foreboding enemy to keep the PCs moving along.