Re: changes her plans at the last minute...how to respond?
Forget about this being a test for one moment and seriously consider what i'm about to say. This girl may actually have plans with her friend. So don't think that she is sacking you off for no reason. In fact you should be calm and collected about it. Text her something along these lines:
"Hey, thats cool, in fact I was going to ask last night if we could meet up at a later date but I didn't have my phone on me at the time :P. Instead keep me company (Insert place, date and time.etc and name) x"
Just make sure you realise that if she was easy and didn't cancel, then she wouldn't be as much fun :P and the above text would demonstrate intrigue, calmness, authority and damn, she will really want to know what you did last night that meant you hadn't your phone :P
Work hard, Play hard players! Oh and Man up, girls like men.