Retrieving request message (the calling command)

I'm trying to retrieve the actual command string of the the command that was used to invoke my program - the CPP. Using QMHRCVPM or RCVMSG I can retrieve the request message with the command string in the message data but ONLY if the command is entered on a command line. If the command was invoked from a CLP there's nothing there. I've looked up and down the stack. Its obviously around somewhere and I could have sworn I've done this before. Anyone know what the difference is between the way a command is processed in these two scenarios and where I might find my command?