My friend violated his federal probation and was picked up Tuesday by the USM and brought to the county jail. It now says he was transferred to an unknown facility. I haven't heard from him anymore yet. How can I find out where he is? And when I check bop.gov it says his original release date from 2014?

You will not know until his movements have ceased unless he calls you from one of the locations where he is being held. The US Marshal Service is very quiet about inmate movements for security and safety reasons. If he was on supervised release and violated, he will have to go before the original sentencing judge for his next determination. The 2014 release date means nothing after a violation.  It is likely he will be in the county jail of that jurisdiction or if there is a federal facility near the court, he will be heading there.