Furthermore, I usually leave a big separate bowl of water and another of dry food when we take long weekend trips, but this time, I just didn't have the time for the big water bowl.
Now, yes, in principle, they could drink from the toilets, but they don't. And Lioth does kind of know how to turn the bath tap on, but I don't know if he'd think to do that if they are thirsty.
We are usually only gone for 48 hours, which would be bad, but probably not fatal.