Letter Sent Via Ballon Returns 15 years later by way of Fish

I noticed another interesting story from Friday. It turns out that fifteen years ago a school in Japan was celebrating its 120th year in operation and as part of their celebration the school had their students write short notes, attach those notes to balloons and send them skyward. The notes had a simple message - something like "My name is ________ and I am a student at ________school. We are celebrating our 120th year! Please send a return note." One balloon with such a note sailed at least 93miles away over the ocean popped and eventually came to rest on a sticky fish. Fifteen years later a fisherman caught the fish and returned the note. The young lady that wrote the note is now 21 years old and in college. Pretty interesting. I wonder what kind of pen that note was written with and what kind of paper was used? I think this story would make a good pen commercial for sharpie or some other pen company.