Yet another 9/11 anniversary has come and gone. Like many Americans, Beatrice Jethroe of East St. Louis, Ill. reflected on one of the darkest days in U.S. history, but her memories from 16 years ago are also different.

“The mystery,” said Jethroe. “The mystery. Who wrote it? How did it get here?”

From an envelope marked 'the floating 9/11 dollar', Jethroe pulls out a one dollar bill with cryptic writing: '102nd F.W. OTIS ANG CAPE COD MASSACHUSETT FIRST ON SCENE OVER W.T.C 9/11/01 F-15’s RULE. YEA!!'

Several days after September 11, 2001, Jethroe’s then 10-year old son found the dollar bill on an East St. Louis street. He tried to buy candy at his favorite store, but the dollar was refused because of all of the writing on the face side of the bill.

“He said, ‘Mom, I don’t want this dollar because it’s written all over it and nobody would take it,’” said Jethroe. “So eventually I gave him another dollar.”

Jethroe tucked the unwanted dollar bill in a drawer where it was forgotten for 7 or 8 years. When a 9/11 anniversary came around, she remembered the dollar and pulled it from the drawer.

“When I saw that 'W.T.C 9/11/01', that made me start showing more interest in the dollar.”

Jethroe’s sister suggested an internet search for answers. “We put in 'first on scene over the World Trade Center.' Once we put it in, we came up with the two guys’ names and once we saw that we started matching up everything on there.”

The two guys are named Timothy Duffy and Daniel Nash, the F-15 jet pilots who were the first to fly to the World Trade Center after the terrorist attacks. Slowly the riddle unraveled. Duffy and Nash belonged to the 102nd Fighter Wing from Otis Air National Guard Base in Cape Cod, Massachusetts.

More questions remained. Who wrote on the dollar, and why? How did it get to East St. Louis? Jethroe said she contacted CNN, and several St. Louis television stations. She said 5 On Your Side was the only one to respond.

KSDK tracked down Daniel Nash, who said he didn’t write on the dollar and was confident pilot Timothy Duffy didn’t either. He theorized a member of his flight crew may have been responsible, but there is no proof of that.

So the mystery continues for Jethroe.

“Trying to find closure. It will help me find closure,” said Jethroe. “I would like to meet the people that wrote on the dollar.”