Does using a VPN mean you can't be traced?

Nope.  You're more challenging to trace, but it can be done.  There is no such thing as being 100% anonymous on the Internet.  Using various technologies, like a VPN, make it harder to find the source, but it can still be done.  VPN leaves a crumb trail.

Bottom line, it's impossible to 100% anonymous on the Internet.

noep. it just means the trace will lead to the VPN's network instead, and they will give the info out when pressured...