Hi Scott!
OK, so this is just a theory, but stay with me...
Have you set up a Recorder Policy to record these calls?
Proactive recording means that it records all calls and then only keeps the ones it is told to. The idea being that if the "trigger" (say. Analyzer detecting the agent dropping an F-Bomb) happens later in the call, you actually have the call recorded from the start.
What I think may be happening is that it is recording these calls, but if your policies are set up to record all calls to a particular Workgroup / Station / User then any that abandon in the IVR (possibly including if they were in Queue, but not yet assigned, but I'm not certain) then Recorder sees no reason to keep the recording and deletes it.
Try setting it to record all calls on the line (in the Policy) and see if that helps.
Like I said though - just a theory, I'm not a Recorder expert!