Having no memory of an event is a common experience after a traumatic experience. It can also be a side effect (or intended effect) of the consumption of a drug or alcohol.
If your child does not remember what happened, do not push them to try to recall what happened. Blocking out a memory is a coping mechanism to help deal with a traumatic experience and trying to access those memories may be retraumatizing if not done with the assistance of the proper therapeutic methods.
If you believe your child was given a drug without their knowledge by an aggressor, take them to an emergency room where they can have their blood taken for testing. Drugs commonly used in this manner (sometimes referred to as “date rape drugs”) often leave the system quickly, so the sooner this is done, the more accurate the test will be.
Drugs taken voluntarily will also likely show up on these kinds of tests. If sexual violence (including attempted) is involved, law enforcement’s best practice is to prioritize the report of sexual violence and not charge the reporting individual with personal use of illegal substances.