How to report this guy ?

This guy named taoci was selling plat sayin he can make gold into plat but disappeared before I could click on him.

Email support about the matter.

Email support with as much detail as possible e.g time, day,where you were, his name..... Things like that.

dont say names bud :)

That is real bad. You need to email support at
Support@spacetimestudios.com

Use as much detail as you can and a tip for the future: Do not mention peoples names on forums. Should be kept between you and the developers.

You can also type "/report <name> <reason>"
You do not need to tap on him. His name in your chat log is enough to enter that into your /report command.