I went out with a friend last week, and he invited 2 girls that he works with to come out with us. These two girls work in another state selling products to different accounts. He refers to them as coworkers. Which I totally disagree. They work in a different state selling to different accounts. I want to take one of them down. He doesn't want me to, and he's not helping with the situation. I want to FB her, but he doesnt want to give me her last name. I feel he's being a douchebag/cockblocker. I know there are other girls to go after, but I feel he's ruining this chance that I have.

This shouldn't be a matter of who is right or wrong. Right now if we tell you you're right that doesn't accomplish anything.
There are a couple things to consider
1) Is your friend interested in the coworker? (and judge by his body language when you ask about her (see if he gets defensive) or if his body language changes when you bring up the matter of you trying to sleep with her that he gets defensive)
2) Is his reputation on the line in any way (are these coworkers possibly going to be coming to the state again/moving to the state/getting a promo any time soon)
3) Buddy just drop it. He was good enough to take you out with him to meet these ladies and if you make a big deal about it this time he probably won't bring you along next time. If you suck up your pride and say 'alright sorry man' he'll at least see that you were man enough to apologize. Don't forget, you had the opportunity to snag her number or last name for fb when you went out for drinks the first time and didn't close. It's not your buddies job to pass that along (even though it is a bit of a douche move and I wouldn't have hesitated to give it to you.)

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You miss 100% of the shots you don't take. Let her rip.

What makes you think you have a chance? Adding a girl on facebook and a chance are two totally different things!

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I should've snagged her number before I left. I'll let it go.

I only add girls to FB if I consider them a friend. I don't use that for chatting up women.

Honestly, follow the bro code. He obviously doesn't want you to do anything with those girls so respect that. Either he likes one of them and doesn't want to let on that he does or he really does consider them co-workers and is uncomfortable with you moving in on them. If that's the case don't be an ass, just let it go and respect your bro.

Worst thing you can ever do is disrespect your wing. Don't ever do it. Ever.

I you really had a chance you would already know her name yourself and added her to FB long before you said goodbye to her. So forget about her until you meet her again, if ever.

If he's a good friend and he has never betrayed you, just back off.
I'd rather have a great friend than have sex with one of his co-workers.
He's obviously upset about the idea of you going after them because that will either make him ruin a chance with them or would damage him in a way.

So I'd have to say no, back off.