It means that you’re in the “maybe call” pile. Sure, he might put you in his phone later. But why not just add you right then and there? Or do the whole, “you call me, then I’ll have your number in my phone” thing. Okay, maybe he doesn’t want to give you his number right away. But putting you in his phone isn’t a huge commitment or anything. Back in the days when nobody knew how to use cell phones, maybe it was. But how hard is it to enter a number and a name?
Honestly, unless you don’t have your phone for some reason, who writes down numbers on paper anymore? Even if you only go out with someone once, it’s simple enough to delete their number later. If I write something down on a slip of paper, I’m gonna lose it. Plain and simple. I’ll put everyone from my closest friends to the movers I used once in my phone. But I’m also absentminded and lose everything. Maybe he’s really good at keeping track of random scraps of paper. Or maybe he hates the environment and wants to waste an entire piece of paper when he can just punch a few numbers into his amazing talking device.
I would approach with caution on this one. He might surprise you, and the whole writing your number down on paper thing was from nervousness or some weird predilection about his phone. Maybe the phone is new and he isn’t comfortable with using it. But I am leaning towards this being a sign that he’s not going to call, and also probably isn’t worth your time. If he can’t punch in a few digits, he’s probably lacking in other areas.
Wait, hold up…was he wasted at the time? Because I definitely have problems doing anything phone-related when drunk. (I’ve sent out drunk texts that read like ransom notes or the ravings of an insane person.) If he was drunk and scrawled it on a piece of paper, he gets a pass. But then you have to wonder if he’ll remember whose number it is the next day. So you might be in for an awkward call pretty soon…