Well, there are very nice porphyry columns in a church (if memory serves) St Petersburg, presumably obtained either from a dismantled Byzantine site after the Turkish conquest, or commercially during Turkish domination of the Middle East. Also, King Farouk had some quarrying done.
It would be nice to acquire some of the scrap pieces the Romans left behind for museums outside Egypt, since they aren't of much interest otherwise (no tourist traffic up to either site). For those who are very ambitious, there's a 200 ton cracked column up there, probably an "oops" quarried for a project of (I think) Caligula. There were others which made the trip to Rome (obviously by water).
I'd be very surprised if some newly-quarried finished objects of great size didn't lay on the bottom of the Mediterranean, and out of Egyptian jurisdiction.
I wouldn't be surprised if that was so.