Dental question

My son went to his dentist to have sealants on his molars then he moved a bit and the paper towel he had on his chest fell on the floor the helper put it back on him, and later same paper towel was used to clean the tool that was putting the sealant on his molar.
I did not say anything because at the moment I thought they were going to put a new one, but after that day I got concerned about bacterias getting in the sealants. I am very concerned because it was very anti-hygienic and the dentist doesn't even know because the helpers were doing the procedure, he was not in the room. Could you help me?