Sounds like you didn't have enough comfort built for her to want to continue interacting with you. However, it sounds like your attraction game was on point.
When asking for a number I personally wouldn't use "Would it be okay if I called you sometime?" At this point she has the opportunity to say no. Don't ask permission to get her number, and do your job so to speak. Just say something along the lines of, "What is a number I can call you at." OR "How can we continue this conversation?" Or just slide her your phone and don't say anything (just smile and assume she'll put your # in). Just don't ask if it's okay if you get it please. Glad you got the # though.
Sorry about the phone close rant, good luck on your next interaction and try to build about 15 minutes of comfort if you can before getting her # this way you are more likely to get a Day 2. She has to know you a little bit and what you are like. She has to be comfortable with you. She meets a lot of guys in the bar she's attracted to. When you build comfort you go from well he's some cute guy in a bar I met to being...Ranger83 a cute guy with views on x & y, and interesting because he is into a & b.
peace