If you are using https://wiki.jenkins-ci.org/display/JENKINS/Managed+Script+Plugin and the https://wiki.jenkins-ci.org/display/JENKINS/SCM+Sync+configuration+plugin
You will have to add a Manual synchronization includes:
buildstep-config-files.xml
to get it to save the managed files configuration. Otherwise all your managed script files you share across jobs will be lost if you lose the jenkins server and have to rebuild it.