This page has the table showing what you should and should not be able to see:
I assume you're talking about an attack-only from a fogged territory to a territory you can see. So look at the line that says "Fogged to Visible".
Now, you're asking about whether or not you should be able to see the number of armies transferred or attacking. The table on the top says this is column 4.
The value in this cell says Success - above the table tells you that this means "Players can only see this action if the order was successful. In other words, a transfer that executed or an attack that resulted in ownership changing."
I assume you're also talking about an attack-only attack that didn't happen, since they couldn't attack. Therefore, the answer to your question is no.