Instead of taking her number couldnt you have bounced her for a date straight after the approach ?. Take her for a coffee, drink, pizza ? or back home ?
Maybe at that point you became too concerned about how the outcome would play out... you didn't want to hear a "no". You get on a roll with the girl, things feel like they're going well, but you don't close because you feel that could disrupt your streak. It's when you feel that "things are going great" that you become most hesitant to get the number because "you don't want to mess it up". ... Dependence on the outcome. It's like not scratching the lottery ticket because you're so afraid you might not have that winning number. It just feels better to hold the ticket in your hand and bask in the possibilities in your imagination. You've got to get to a point where you literally don't care if the girl tells you to fuck off.
