Had sexual activity via hand and penis of partner who gets genital herpes. then changed baby's nappy forgetting to wash hands. will my baby catch it?

No: Herpes spreads by skin-to-skin direct contact, ie, directly from the site of infection to the site of contact. Cloth, etc in-between interrupts it as does air/time. Stil, hand-washing after sex is a good idea as is pre/post baby diaper contact but don't obsess on it. Why unprotected sex? Are you trying to conceive again - so soon? Are you trying to get an STD? Protection is important. Take care!

Unlikely: If your partner did not have active lesions at time of activity it's unlikely herpes can be spread