Do Process Servers also investigate?

My husband has filed for divorce. For the past two weeks a process server has come twice, once two weeks ago and another exactly a week later but I have not been home either time. She has left her card no name or addressed to anyone but I ume it is for me pending my filed divorce. I have called her off the hook left her voicemails and no reponse. Yesterday my neighbors said they saw a man parked infront of my house with a professional camera and zooming in and taking pictures of my house. My question is can the process server be investigating me because they believe I'm avoiding them when clearly I'm not or could it just simply be that my husband hired a private investigator? The man did not get off the vehicle and ask my neighbors questions or ring my doorbell...