That's funny, I've been doing something similar, trying to get in touch with a really good friend who I used to go to school with but haven't seen in 2 years. Problem is that his cell phone # is probably outdated so I haven't tried, and no one picks up at his home phone, probably on vacation. I called about 1 pm every day for like 6 consecutive days, then stopped for a few days, then called again, then the next day after that I called at about 9 am to see if that would work, and I plan to try calling him again a couple more times after waiting another week or so.
The biggest problem is that I deleted my facebook for self-respect/moral reasons many months ago, and with the NSA scandal there's no way I'm going back to that or to twitter for that matter.
So I would say keep calling, 3 days is nothing compared to what I've been doing. I sure wouldn't want any of my old friends to give up on me so easily.
Then again, I'm talking about a person who was my best friend ever (and I'm pretty sure I was his best friend ever, but that might be an arrogant claim to make) whereas you seem to be talking about someone you just met, or haven't even met. Hmmm, but still, it can't be creepy if it's for a good purpose, especially if you haven't even managed to reach the person yet. I mean if he told you to fuck off that would be that, but if you haven't reached him yet then I'd say it isn't creepy so keep going.