If your CrashPlan application has disappeared / gone missing / vanished then please follow the instructions below to reinstall the client.
Log in from here (your username is your email address) https://code42.ceejay.net:4285/ and click on App Downloads at the left of the screen. Now click to download the latest installer for the operating system you are using. In this case it is Mac OS X and Version 6.5.2.
Once downloaded, install the CrashPlan client. If the installer does not open try downloading the installer to a different location such as your Desktop.
And once installed, reboot the machine you are using.
Once rebooted, open up the CrashPlan client and log in. If you are asked for the server address, enter: code42.ceejay.net:4282