I would, essentially, be using magic to check the... let's call it the metadata, of your memories. To see if they were tampered with.
There are, as I see it, three main potential situations:
1.) He hasn't interfered, and you've forgotten.
2.) He has, but he isn't very good at it. If I wanted someone not to know my name, I would have remembered to alter the memories of you receiving it, not just the name itself. If this is the case, it isn't a problem and is easily fixable.
3.) He has interfered and he's checking our capabilities, which is the situation I would find the most worrying as it would most likely mean the questions weren't honest ones. I dislike being toyed with.