I recently learned the hard way, when a girl's IL is low to moderate, then never ask her out on the weekends. Just stick the the weekdays. During a conversation, if she mentions a particular day as a possibility, move in for the close by offering place and time.
If she stood you up, don't even bring it up. Just wait a week or two before calling her again and ask her out for a weekday date. Then just concentrate on having fun with her. Don't let the blowoff get into your head.
In the meantime, do all you can to collect more phone numbers and date more girls to keep the obsession of 1-itis away, to prevent you from doing anything desperate or stupid.
With girls with low to moderate IL, they will act flakey, don't let that crap get into your head. Don't take it personally, you are not obligated to eachother, so you don't have the right to do that.