The attacker was known to the victim, West Mercia police said.
Officers believe there were people in the parking lot at the time and that a member of the public may have approached the victim.
The force calls for the individual, or any other person likely to have information or images of the attack, to present themselves.
Anyone with information should contact the Sian Evans PC via 101, quoting the incident reference number 599 of July 14, 2020.
You can also contact Crimestoppers anonymously on 0800 555 111 or crimestoppers-uk.org