My friend apparently got in touch with the stranger at a bar that is known to have a lot of bitcoiners around.
Yes, get in touch with the Police right away, the sooner the better. If he actually met the person in a bar, there very well might be surveillance video of the person in question, or at least of him walking in/out of the place that your friend can review with the police and help identify him. But, some establishments overwrite their tapes or hard drives as they fill up, so the sooner you act the better the chance that this type of evidence will still exist. Also, there may be other people who frequent the bar, or one of the bartenders or waitresses that might know who this stranger is, but again this would be more of a job for the Police. The amount involved makes it a significant enough crime you may actually get someone out there to investigate the place and snoop around, as if he ripped you off he very well may have ripped others off as well.