A little neediness. For writing her number on that thing means you need her. Women don't like men that need them. Yes, it's good to switch to boring conversations after 3 humor, but don't stay there too long.
Start with humor, move to naughty or sensual conversation, then boring. Before you know it, be the first to take an excuse to leave. In your case, you didn't take any excuse (time constraint) to leave.
When you take an excuse to leave, you'll appear valuable and busy. Women love men who are busy. When you're always looking for a way to stay with her, you lose all your value. In your case, you lied to yourself just to follow her. That is neediness, but you won't know.
In this relationship game, it's not always about what you say, but how you say them and what you didn't say.
What you didn't say = bad boy and non-needy body language.
Your body language says a lot. Don't focus on only what to say, but how you carry yourself with confidence and I-don't-care behavior + challenge and mystery.
Always be the first to leave even if you've just spent 50 seconds. Even if you don't want to leave, make a statement that shows you're in a hurry and will be leaving her soon.
This statement is called time constraint and when you say it as a fun and naughty guy, the woman you're talking with will wish you don't go.
Has a cousin or relation visited your family before and overstayed until you guys secretly see him as annoying and want him to go? That is how you just behaved.
Has another relations come to visit, but said, "I won't spend more than 2 days because I'll be going to Enugu for something on Friday."
With the person who talked about traveling or not staying for more than two days, your family will wish he stays longer. You'll hear comments like, "Common, Joseph, at least spend a week with us before traveling."
Did you see how your family is begging Joseph to stay, but wanted the first guy to go? That is exactly how women work. The person who appears busy (even if he's faking being busy) is the one women want (hard to get) and not the person who wants follow them everywhere they go (too available).
If you want to follow a lady bumper to bumper, your humor will be seen as clownish and boring.
When you're talking with a woman with naughtiness and humor, always make a statement that indicates you'll be leaving soon even if you don't want to leave.
Women do this a lot when they visit a man. They'll be in his room and the next thing you'll hear is, "I'll be leaving soon to go see my aunt. She said I should come."
No, she's lying. She wants you to value her time and take action — maybe, Sëx or kiss. She wants you to man-up.
If you want to master how this dating game works, switch the table and act to women the same way they act to men and you'll get great results.