I have checked several books on Ira and haven't found any mention of Gottfried Wagner's visit with him. Since it occured in April 1978 shortly after Ira's stroke there are only a couple of books it would be covered in - most of the bios predate that period. Also, it doesn't sound (from the description in the Wagner book) as if it were a very long visit, or a very important one, to Ira anyway. He might just have forgotten about it and not mentioned it in subsequent interviews.