When the car crashes into the unicorn, the airbags fail to deploy. In a real collision of that magnitude, especially involving a mythical creature of such mass, the airbags would almost certainly go off.
The unicorn is hit by the car on it's left side while crossing the road but the big wound is on the right side when it is laying on the ground.
When Ridley is hiding in the car her phone flashes on and the screen clock says 08:24, which is 24 minutes past 8 in the morning, even though it's night time.
A little later, her father's phone says 11:45, which is quarter to 12 in the morning, yet it's night time.
A little later, she uses the torch on her phone and the screen shows 20:30, which is half past 8 at night. As it is now on the 24 hour clock, it shows that the previous times were incorrect.
Near the end just before they go outside for the last time, it goes from night time to bright daylight, even though only 10 or 15 minutes have passed.
When the horn is placed next to the baby unicorn, an ear tag is seen.
The film is set in Canada, but a US hundred dollar bill is shown being rolled up. It's not established what nationality the character is, so it could be accurate.