LOL, if I were you I would straight away just move on after like 3 hours, why waste time where in the same time you can get another girl ? Totally not worth it.
Easy. Next time this happens call the girl right then and there to see if the number is real or not, do it jokingly, of course. Think on your feet, pleb.
text 2h max (except if you've sent your message late, people need to sleep)
email 4 days max
someone interested will respond fast imo and will always find a way to stay in contact (+inform you if they cannot respond to you for a certain period) even if they run out of battery or if their internet is broken