[Travis McGee]

I agree with your analysis. If this was true, the first we would hear would be SEALs have captured them.

[Lion's Cub]

There is one possibility I just thought of, though I don't know enough about ships to know if it's really possible.

I remember reading that the Iranians had purchased a couple of subs that were supposed to be state-of-the-art. I wonder if the configuation of these surface ships is such that they would hide any signal from Iranian subs that were hiding beneath them?