(IS THIS A BUG?) Enemy caught my Spy on my Sub

[GIR]

I don't know if this is a bug but the enemy caught my Spy on MY Submarine.
My Sub was next to his Capital but he wasn't even able to see my sub because of his tech lvl (no destroyers).

 

[ainwood]

Well, a save would be nice.

 

[Ghandi33]

This same thing has happened to me a number of times. They seem to have a chance to catch spies inside their cultural borders regardless if they are on a naval unit or not.