PJ:
You are right that the red bumps you described do not sound like herpes. Herpes produces blisters which last 5 to 10 days, rather than coming or going as quickly as the once you had. Yeast is not likely either. most probably, you had a mild irritation or dermatitis, which is quite common after friction whether from sex or otherwise. If you get it again, try hydrocortisone; if that works in short order, dermatitis is almost certainly the problem.
Best.
Dr. R
Dr. R