It's pretty common to treat unauthorised entry attempts as a serious security incident. The minimum follow-up actions I'd expect would be filing a police repor

It's pretty common to treat unauthorised entry attempts as a serious security incident. The minimum follow-up actions I'd expect would be filing a police report, sending all-staff emails reminding people to be on the lookout for tailgaters, and reviewing security at reception. If there was a specific risk of ongoing intrusion attempts, then I'd also expect legal action (eg. injunctions or restraining orders) to be taken in mitigation. It's perfectly reasonable for staff to want to seek assurance that those sort of basic measures to ensure their safety are underway.