Long straight hair gets in food pretty frequently, but you know there’s a problem if the hair is short & curly. 
Kinda along those lines, I figure that my mouth gets on a woman’s crotch once in a while and that’s probably more contaminated than anything that could be on a hair in the food.
(Full disclosure: for those who don’t know, I am a health inspector.)
This is off-topic, but what is WITH Olive Garden and foreign objects in food? I know two people that have found obvious non-food items in their food at a restaurant, and both times it was Olive Garden. MrWhatsit found part of a plastic bag in his salad there once - and was told, “Oh, that’s the plastic bag the salad came out of,” as though it was no big deal and this sort of thing happens all the time (which apparently it does). And a co-worker of mine actually found a small bolt in her salad there.
That happened to me once but luckily I noticed it immediately while the server was still at our table. I sent it back. I probably got the same plate sans hair but I couldn’t not send it back. Unacceptable.
I discretely move the hair to the side and continue eating. If I am friendly with the owner, I might mention it after I’ve paid the check, just so the owner is aware. If the owner wants to buy me a drink for my troubles, I retire to the bar.
I can’t remember ever getting hair in my food in a restaurant. I once found a thumbnail in a salad, though. I wasn’t in the restaurant - I’d had it delivered to the office when I was working late. I called and bitched out the restaurant and the delivery service, and also reported them to the health department.