What happens now if you gave your underage sister who looks just like you your CO drivers license for her to be served at bar but they took the license?

You sure got yourself in a pickle, as the saying goes. You could try contacting the bar establishment first. However, you will likely need to present other photo ID and another way to prove who you are to the bar management. If you go this route, it would probably help considerably if you dress in your most professional outfit or look very presentable, like going on a job interview. Be very polite and apologetic that your sister tried to fool them. They will likely want to know 1. How your sister got your license and 2. How did you know where your license ended up... Do you have an answer....(It really won't help much to tell the bar you let your sister have your license!) IF you can answer those questions satisfactorily, maybe (big maybe) you can convince the owner or manager to allow you to claim it. OR, they will inform you of the procedure you must follow to claim it. Again, be very polite; don't swear or threaten them, because the bartender was only following the Law. If all else fails, contact a lawyer or your Bureau of Motor Vehicles for advice. Of course, you want to protect your sister--but perhaps both of you will suffer the consequences of this act. Reminds me of something stupid I did in 9th grade in Art Class (of all things)... embarrassed, I had to face the consequences of my action.