Marc - You're right that dialing 011 before 954 doesn't seem to make sense, as 011 is the code used before a foreign country code when dialing from the U.S. to a number abroad. 001 is used when calling to the U.S. from aboard, as 00 is the access for international lines and 1 is the country code for the U.S. It appears that Silversea is confused about its own system.
In any event, another option for emergency calls to the ship from the U.S. is to have your family use the Dial A Ship system suggested on the Silversea website:
http://dialaship.com/Silversea participates in the system, along with many other cruiselines, including Regent. We've tried it with Regent; and it worked well. The caller needs to have a credit card to make the call. Otherwise, one simply follows the prompts after dialing the toll-free number to choose the correct ship. The procedure is described on the Dial A Ship website.
If you are not certain that it will work when the ship is in a remote area, you could give it a try when Silver Explorer is somewhere remote. When I used it with Regent, the ship was not in a remote area.
Cheers, Fred