Even I have come near losing a glider in the toilet in the past. It is an all too real possibility for critters that climb and leap.
When I found my sickly brushtail possum dead in her cage, knowing that they can torpor, I went out of my way to move her, shake her, warm her up and so forth for just this reason. Alas, she drowned herself in less than an inch of water as she had a seizure. Her lungs were filled with water and there was no coming back. sigh...
Animals arent easy and it is hard to always think of everything. So for most folks, it's a constant learning and relearning adventure. You have to work hard to protect the ones you love.
Strangely, as far as animal husbandry goes, sugar gliders have been the easiest of any exotic animal I have tried to keep.