How likely to get pregnant in one sexual encounter and if you pull out correctly without any semen getting out?

Enough of a chance that I would use a condom in the future if you don't want a baby.

You can't know if anything came out. You can't feel pre-ejaculate being released. If you're erect, you release pre-ejaculate. That's just how it works. If you try to argue with that, you prove you don't know enough about sex to be having sex.

Yes, she could be pregnant.

Every pregnancy is the result of ONE act of sex.

And yes, if she was fertile, the odds might be as high as 25-30%

And there is NO way you could have 'been sure nothing got out.' If you were erect enough to penetrate, you were releasing small amounts of semen.

Presumably, before you embarked on this one night stand, you and this random girl both got tested for STIs, waited for the results to come back, and both agreed that you were perfectly fine with an unplanned pregnancy, and would, therefore, forego any actual contraception?

There is always a chance dude... it is risky business. I suggest you invest in some condoms and then make sure you use them every time.... the worry and anxiety you are feeling is just not worth it. And you should use an antibacterial penis health creme like Man1 Man Oil to improve hygiene down there... this will add to her pleasure, give you confidence and decrease the chances of odor and infections.... these cremes are great. Hope this helps and good luck.