Why is he not talking to me all of a sudden?

So 2 weeks ago, I met this guy on this iphone dating app called Tinder (which is pretty popular) We exchanged numbers and texted A LOT for the first few days. However, the last time i texted him was friday night:

Me: Sorry i drunk texted you!
Him: Lol no i was rolling (popping E)
Me: I thought you said you were going to quit? Lol

That was the last message i sent him and it's been 3 days I haven't heard from him. Did he lose interest? Or does he need space?

I'm 19 and he's 24. He's not THAT busy because he's unemployed… And he uses his phone alot because he's been using facebook on his iphone.

I was never clingy to him. It was usually him who texted me first. But after the first few days, we've been texting a lot less.

But he did told me in the first few days we were talking that he's going to take me out on a date when i go back to SF on friday. Should i message him when I go back about the date? Or should i forget about it?

You're worried about losing a drug addict who you've only known for two weeks and who is being uncommunicative? Be happy.

Well he seems like a loser, so why waste your time worrying about his opinion?
If you really feel like you want to get involved with him then keep it cool. Don't message him. If he wants to take you on that date, he'll text you. You shouldn't have to make all the effort. Play a little hard to get.

Hes most likely busy, met someone else, or doesn't feel a connection towards you anymore. If you want to score a date, talk to him about one, or wait until he talks to you again which is about a 30% chance. And don't come off clingy or needy if you do.

Just forget about it, if a guy wants a girl, he'll cling on her, you can say maybe he is out of materials but, that's not an excuse, though, search for another one

Just forget it, I think you should see someone your age who understands you more not just random guy whom you know nothing about! He could be a dangerous guy or a creep for all you know! Plus "popping E"?! That alone is a sign to forget about this guy.

Well as you already mentioned that you were never so clingy to him then what does it matter whether he text you again or not. Also since he was the first to text you he must show interest in taking you on date. But now he has not texted you so it is better not to text him or in simply just forget him. In case you don't feel comfortable in forgetting him then just wait for his text or remind him of date that he said will be doing with you once you are back to SF.
Either way have fun