> Unfortunately the part about my department letting students go to the bathroom during exams with their phones was true, and is still true to this day

...what else can you do? You could confiscate phones before a test, but a student who was determined to cheat could have two phones.

Do you not allow students to use the bathroom? Do you give them a pat-down before and after they leave the room? Both are plausible strategies I suppose, but strike me as highly invasive.