The syringe, which was caked with dried blood, pierced through the mattress cover and poked Emily Smith's right heel as she crawled into her bunk bed at Guest House Inn and Suites.
"There were syringes, plastic bag, bloody bandage all underneath the mattress cover. We were really shocked and freaking out," said mother Angie Smith. "It scared us to death."
Now the family wants to know how it got there, and what health risks the girl faces.
"Our main concern is HIV disease, and hepatitis B or C," said the girl's mother.
But a hospital told them it could take a year before doctors know for sure whether the girl has contracted any disease; the family was told the girl would need regular blood work for 12 months before they can be sure she is OK.
Emily, a shortstop with a fast-pitch team, was in Aberdeen for a tournament. The family stayed at the hotel another night, and was angry to learn the hotel charged them for the room despite the incident.
"Their answer was, 'No, we're going to investigate like we did something wrong. That's why we're we are so upset. We are not in the wrong here," said Angie Smith.
However, the hotel told KOMO News they contacted police immediately.
The hotel's general manager said staff members contacted police immediately, but will not refund the family until they determine exactly how the needle got under the mattress cover.
The manager called the incident "a horrible situation."
"We have launched an internal investigation. The staff is on high alert, and we've done a clean sweep of the hotel," said manager Angel Housden.
The manager added the hotel offered to move the family to another room and conduct a security sweep of the first room, but the family declined.