Syphilis is not that common in developed countries which lowers the risk anyway. For it to transfer to someone else, the original sore on the infected person (the chancre) needs to be rubbed quite hard to the other person for it to transmit. The mouth area is protected by saliva which contains certain enzymes which help kill off foreign bodies such as bacteria and viruses.
Most people if they see a sore would not go out and stick it in places for 1) fear of spreading and 2) embarrassment.
Even if he did have syphilis, most labs in these developed countries have up to date testing equipment where the old 12 week window period is outdated and the test are good from 6 weeks. You are 2 weeks over this.
If you google window periods, you will see all sorts of numbers from 4 to 12 weeks. Some places are more conservative or are guided by old guidelines or religious beliefs and others just air on the side of caution. In my experience, I go from the following: