We had a wonderful experience with Fun Under the Sun Watersports. The Jet ski's are awsome. My daughter got a little banged up but she said she loved them. My son went on the banana boat ride.
The tent is located between the Holiday Inn and the Playa Linda Resort where we stayed. The high winds may have blown the sign down. I saw it on the side of the tent. As for the hotels knowing the name, I think the hotels only know the BIG companies out there. The hotels can't know all of the names of the tents up and down the beach. As for your cell phone not working you could have used the hotel phone's to call them. Maybe you should try Cingular as your carrier they have good prices and reception.
Can't wait until May when we go again. We will be using Fun under the Sun but this time I will book on line. We want to do the Catamaran Snorkel and my daughter wants to try Parasailing. It trully was FUN UNDER THE SUN!

Be happy! Aruba is one happy island!!!!