Of all the types of injuries a person can sustain, head injuries tend to be the scariest. Scientists have learned a lot about how the human brain works, but there are still many uncertainties. That’s especially true when it comes to brain injuries, where a person can appear medically healthy but still exhibit dramatic cognitive symptoms.

16-year-old Riley Horner was a happy, healthy Illinois teen when she was struck in the head on June 11th of this year. Her injury — an accidental kick in the head from a fellow student who was crowd surfing at an event — resulted in what doctors initially believed was a concussion, but every day since, she’s woken up believing it was June 11th.

Horner’s memory never recovered, and as WQAD reports, the teen can remember things for about two hours before it all disappears. Doctors are stumped, since brain scans have revealed nothing, highlighting how incredibly difficult it can be to diagnose brain trauma.

To cope with her memory troubles, Horner carries a notebook where she jots down details of her day that she can read back when needed. She sets an alarm on her phone to remind her to read over her notes every two hours. Her parents are, understandably, struggling with the uncertainty of what lies ahead.

In an interview with WQAD, the teen and her mother explain that waking up and realizing it’s September, not June, is a daily struggle.

Meanwhile, there is little doctors can do but monitor the situation and hope that any damage done to Horner’s brain can be reversed naturally, allowing her to form memories once again. Cases of memory loss due to brain trauma can improve over time, and Horner’s family is hopeful that the same may be true for their daughter.