Online a selling for used underwear (specifically thongs) that had been worn before in good used condition ive never had used underwear before & wont again. i washed, but could i get herpes from wearing previously worn thongs by an unknown person?

That is very unlikely since the thong would have been washed. However, stick to new underwear and remember that the risk for vaginal infections increase with thong wearers when they remain in place for several hours as they pick up bacteria from the anal area and transfer it to the vagina. In my practice, I often tell thong wearing patients with repeat infections, "Don't be a 'crack' addict."

No, herpes transmission is not possible in above scenario. Check cdc.gov for reliable information regarding herpes transmission.