In general, it is not considered appropriate to call an employer and ask if someone works there unless you have a valid reason or a specific relationship with the person in question. Here are some situations where it may be acceptable:
Job Reference Check: If the person you are inquiring about has listed you as a reference on their job application, it is reasonable for the potential employer to call and verify the information you provided.
Background Check: Employers may contact previous employers during the hiring process to verify a candidate's work history and job performance.
Personal Relationship: If you have a personal relationship with the employee, and you need to get in touch with them urgently, you may contact the employer to ask for their current contact information. However, this should be done discreetly and with the employee's permission if possible.
In any case, it's essential to respect the individual's privacy and the employer's time. If you are not directly involved in the hiring process or have a valid reason for contacting the employer, it's best to refrain from making such inquiries. If you need to reach someone, it's generally better to try other means of communication, such as email or social media, if you have their consent to do so.