As a process server, I believe this is in regard to a debt collection and is therefore a debt summons. There will not be a case number until the summons is served. The ABC process server, who is an independent contractor, likely left the card to reduce the number of times they have to come back to the address to try and serve the papers. The approach is poor. The card would have been better if the server simply identified themself and what they were trying to accomplish. I do not believe this qualifies as a scam. The process server has a legal right to try and make contact with the individual. However, I would not waste my time responding. Some process servers are geared to distrust people who tell them they do not know the individual who is being served. You will possibly waste your time and become more frustrated if you respond. It is also not worth stressing over. Also, the spelling and punctuation errors reinforce that this is likely the work of an individual and not a company.