After destroying a Titan Foundry (while a titan is under construction), I found that the Titan, that was being built, seems to stick around for far too long. I suggest that the titan disappears when the fiery explosion subsides, not when the smoke clears up.

During the construction of a Titan in the Titan Foundry, six sparks go off on each of the spikes. After the Titan Foundry is destroyed, these "sparks" seem to stay long after the Titan Foundry is destroyed.

(I would upload the photo, but each time I do, it appears as a long string of text, and not as a picture.)

On a side note - when you click on the Titans icon on a colonized planet (as if you are going to build a titan) while the planet  does not have a Titan Foundry, you will hear "Capital Ship Factory Required." It should be "Titan Foundry Required."