Thanks, and by the way, I didn't run, he asked me almost kindly to just let him go and walk home or else he would harm me. So I let him go, told him that this was a nice way of him to thank me, that he couldn't use the phone anyway as it had a password etc. Then as he walked away I turned around and went home to call the police since I didn't for one minute intend to let him get away, it doesn't matter that I'm subconsciously scared, I will give the police as much info as I can, I'm just not willing to confront him physically as long as he could infect me with HIV.
I do trust my reflexes a lot in some cases although I'm usually a slow person, but even if I could stop him from putting the needle into my throat, he could still get my hand or arm instead etc. Those are things I considered in the few seconds when he pulled it, it's a freaking needle, it's designed to penetrate skin.

That said, I had no idea whether it actually was a needle, he had already lured me to a darker area in a side road and I looked at his hand shortly but couldn't make out much, I had become a bit nervous, the view on his hand was blurry, I pondered the abocve, including it could be a bluff but decided his hand was already too close to my throat and he seemed way too confident of it to risk anything. Keep in mind he probably fooled me to think he was actually calling a friend as well and made me relax a bit when shortly before he pulled the needle he supposedly told the guy what I had just told him to say, that he had another guy's phone and couldn't talk for long. So I expected to get my phone back soon and then he asked whether I was healthy, I expected him to try and run away if I said "no, I'm cranky and miserable and have an artificial knee" so I said I'm fine and then he turned around "you know what, I have...." and so on. In hindsight it seems very clever, he approached me on a big street and lulled me into thinking he was just some weird guy doing a phone call to a friend until we were in a dark place. I wasn't going to use violence for him walking a bit with my phone, but if anyone tries that again (after getting my phone somehow which I won't let anyone take out of my hand anymore) I will bring them down very hard, after all I walked behind him for a bit.

However, next time it may be three muscular guys with knives and guns and balaclavas and then I would rather show that I'm not the worst sprinter...

You don't win such an encounter by being the victorious slayer(although that does have a great appeal, yes, I'm a quiet guy...), you win it by preventing the other guy from getting what he wants and/or getting out mostly unharmed.

I'm happy that he didn't ask for my wallet for example, as the policeman said, it is easier to keep in your hand what you already have than take it from someone, I should have stopped him more thoroughly from grabbing the phone in the first place, that much I admit, but afterwards you always know better as we say.