The prosecution can amend the 18.2-750.1 to 18.2-250.1. The words Possession of Marijuana were probably written on your summons next to the Virginia Code Section. DO NOT expect to win on this issue.
You were not in ACTUAL POSSESSION but rather CONSTRUCTIVE POSSESSION.
Your statement to the police (if any) and any other factors (evidence) will determine whether the evidence is sufficient to prove the allegation.
Sounds like you MAY have a defendable case. Get a Danville Lawyer!