Can a stalker who puts something online be traced?
Absolutely, everything you do online is tagged with an IP number (internet protocol) including emails, what searches or websites you look at, if you post something online, create a fake profile etc.
When you read stories about a peadophile being arrested for downloading illegal photos. The police traced their online activity to make those arrests. The same process can be used to trace a stalker.
However, the police do not trace every stalking incident.