You don't find anything reflective enough to signal the Gallant, however a piece of yellowed sail tied to an oar gets their attention.

"Seems you had an adventure in there," he says with a grin when he spots the half-orc prisoner. "We'll get the ships in the sea and out of the raiders' hands. I'm guessing we're taking this fellow too? Guess I can send one of our capture ships back to Aundair with him...."

The other sailors move into the cave and start to get the first ship ready to row out into open waters.