The tools included two long pieces of wood, duct tape, and a "grabber". I wrapped the duct tape (Gorilla brand) around the ends of the wood (inside out) reached down the nearly five feet into the drain, and, using a chopstick technique, pulled the phone up as far as the strange angle and thin holes in the grating would allow. I then had my helper (a passerby) use the "grabber" to grab the phone, though it was still impossible to just raise the phone out of the abyss. Using my forefinger and middle finger, I was then able to fish the phone out of the hole.
This was quite an adventure, which luckily turned out well, thus ensuring that my Monday morning was brilliant and wonderful rather than annoying and expensive.
Although this all turned out well, I do hope that this saga (which began months ago, when my phone took a brief swim in a urinal) is now over, and that my phone and I can now settle into a humdrum, happy life together, devoid of adventure and danger.