My head is itchy just from reading this thread!!
DD got lice a year ago. The best thing that we did, was get the prescription stuff from the Dr. Yes, it's a total chemical, but it killed them once & for all!!
Now, we wash hair every other day & hairspray it every day. Most of the time it's pulled back as well.
Personally, I wouldn't go to someone's house that I knew just had lice, because although you may bag up and/or wash everything, someone else might not.
One more thing, if you've never seen them before, then you really have no idea what you are looking for. I thought I had seen them in DD's head, but it wasn't them. The school nurse pointed them out to me.
Good luck!