What a cute game! Love the colour palette used, and the art is all very charming!
I also heard this rumour too, but I heard you had to go into the SS Anne, then let your party get wiped out after getting Cut, which stops the boat from leaving. Then, you go and grab Surf and Strength, swim to the island where the truck is and push it to find Mew underneath...
I also did that, but of course, it didn't work haha ;;
It's pretty interesting how this specific rumour became so widely circulated; I wonder where it originated from...