Its better to have a Jive Project and all your customizations on Your local Machine. Along with that, Download the Source Jars .
If You are using Eclipse , then, a Java or File Search of the Content You are looking for , would provide you with the files / ftls that have the Search Term.
Additionally, you can try to identify FTL File with the Source sometimes using FIREBUG tool in Firefox browser.
If the change is just for the FTL or SOY file, then you could make it as a THeme Change and deploy.