@Blake-and-Mattea0 The guest has obviously not even attempted to hold you responsible, not asked for a refund, and left you a 5* review. So why would you even consider that you might be held responsible? Never issue or offer a refund for something that isn't your fault.
One of my guests had his cell phone and a debit card stolen on the beach when he went for dip. He certainly didn't hold me responsible, nor would it occur to me to think I am.
Nice of you to be concerned, though. I was very sympathetic (without being apologetic) to the guest who was robbed. What was funny is that I was much more upset for him than he was- he managed 10 Dominoes Pizza outlets and said losing the phone was fine- now his employees would leave him in peace during his holiday and have to work out any issues on their own 🙂 And he had made sure the debit card he took to the beach was one that linked to an account with only a small amount of $ in it.
When guests ask me if the 20 minute walk between my place and town/beach is safe, I tell them that none of my guests has ever had a problem, nor have I, that it's a residential area with many homes along the way, but that of course I can't guarantee anyone's safety and that they should exercise the same personal caution they would anywhere.