Ive met girls at bars got their phone # but never called them.. I don't know why but I feel like meeting somewhere besides a bar for me just seems a whole lot better. Maybe its just me but having a conversation at a bar just blows and you can't hear the person your talking to most of the time.
Hence the reason (possibly) that they have given you their phone number is to call them so that you may have a conversation that will be heard. That's providing the fact that the phone number given to you was a real number. Alas you may never know if you have not called someone who has as you've said given you their number. Everyone has their own comfort zone. I have not been in the "bar scene" for quite sometime now, but can understand all the other distractions, problems that are there when trying to communciate, break the ice etc..
Perhaps if you have the opportunity to have phone numbers, you could suggest meeting somewhere quieter to meet in order to have a conversation. Just a thought. Good luck with your search.