Just their Dick and nothing else? I couldn't imagine trying to save someone through a glory hole.
You never know when an adjacent stall is going to catch on fire, trapping someone else. I imagine they would tame the heat while the firefighters arrived.
OK, fine. If there were a fire, a penis may be able to beat it out. I need help thinking of a scenario where hands wouldn't work better though.
They could be tied up, who knows. BDSM doesn't always go according to plan.