Thanks for your question and concern, as you said that you partner told you that he is down with genital herpes simplex 1, as they are of two types ie, type 1 and type2 . The type 1 causes cold sores not the genital herpes and as you mentioned that before doing the oral sex you checked for the genital and penis area and didn’t found any sores then the chances of getting HSV is very low or you can say none. There might be chances of std symptoms in this disease. There are various checkups for HSV Infection. You can go for antibodies test for HSV, a serology test for which you need to wait for 4 weeks for antibodies to form to show a result. According to me I would suggest you to go for a safe sex and use precaution as possible. I hope I have cleared your query. Take care