If they saw lice then that's probably what it is. A lot of lice is resistant to the RID. Get Sargents dog shampoo with the permethrin in it and shampoo with that let it sit on your head a few minutes and rinse. It is stronger than the RID.Use it like two or three times a week. You can also take some ivermectin. You can get the ivermectin horsepaste tubes and put it on your hair like conditioner and let it sit for a 1/2 hour before washing it out. They are now using topical ivermectin to kill resistant lice.

When my daughter started kindergarten 3 years ago, before I started homeschooling, we would get the "someone in your class has head lice" papers every other month. My daughter is in dance classes and does modeling, so she has looooooong hair - down to her butt... so I dreaded the day she would get it and I'd have to treat a head full of THAT hair. Luckily, none of my kids ever got it, and I never had it as a kid so I dont have experience... but I did a ton of reading. The Hair Fairies (lice removal service lol) pretty much say that the ONLY way to get rid of lice is to comb out all the eggs. Like most of these icky parasites, nothing kills their protected eggs from the depths of hell... You have to oil up your scalp and your hair shaft and have someone comb it out in small sections. The oil helps "unglue" it from the hair shaft.
Now, of you think you're dealing with mites, that's a different thing totally. I would follow the advice given here. My friend who has a horse farm uses permethrin to treat mites in their ears... and she swears by it.