Urgent help needed....How to unlock a car that's running?

I lost my master set of keys last week. today, since it was snowing i went out to heat the car up and remove the snow. unfortunately, i locked it. i don't have a spare key. what do i do? i have half tank of gas in it. is it okay if i let it running for a long time like say three hours? also i have turned off the heat full up. should i call the dealership for a key? any suggestions? i am desperate. please give me suggestions. when i was young i have seen my dad use a a steel thin rod to open the door through the bonnet of the car. but i don't think you can do that with this type of honda civic. do you think i can use a drycleaner's hanger to open the door through the dent/open part in the front tire? or should i call a locksmith/carsmith or something?