Can I catch HIV from having frottage in our underwear? (2 men) There was no open mouth kissing...just dry humping in underwear

No risk at all. Definitely there is no risk of HIV or other STD transmission through clothing. HIV is sexually transmitted only by vaginal or anal intercourse. Never by kissing and rarely if ever by oral-genital contact, so this would have been a no risk event even with those contacts. No worries at all about this event. Best wishes and stay safe!