The risk of contracting genital herpes from a one time encounter are very low and really not worth worrying about or testing for. If you are paranoid about it and want to do testing then I recommend a baseline herpes igg blood test now and then repeat it in 4 months after the encounter. Should you develop any obvious genital symptoms before then, see your provider within 24-48 hours of their appearance for a lesion culture and typing.
If this was an unprotected encounter, don't forget to follow up with testing for other std's at the appropriate time too. It's so not all about herpes!
grace
The thing about herpes is you do not have to have signs or symptoms to spread it, and just because you have it does not mean you will spread it! Contracting herpes with out signs or symptoms is called asymptomatic shedding. To understand herpes better you may want to read a book called living and loving with herpes. This maybe able to answer some of you questions. Also remember just because you used a condom dose not mean you will not contract it. I had protected sex and got herpes from a person who was shedding asymptomatically. There are some other factors like does this person take suppression medication? How did you find out this person had herpes? Did they tell you, or did you hear a rumor? Have you ever had an HSV2 blood test in the past? You have to ask for this test, it is not normally part of an STD screening. Most people do not know much about herpes and so many people have one form or the other. HSV1 is oral herpes 80% of the population has this, many with out symptoms. 1 out of 5 people have HSV2 genital herpes, many do not know it. I would say let me know how you found out they have herpes first. Then in about 12weeks you may choose to get a blood test just to know where you stand with HSV. I hope you are fine, but you may take this opportunity to learn more about herpes, it never hurts to be informed. And to answer your questions about odds, well every person is different! There are not really number studies about odd, they are more about factors like monogamy and medication.