It's extremely common actually, and not that surprising considering how much human physical activity is involved in processing tea. Don't worry about it though, a hair (it isn't necessarily
a pubic hair btw, more likely a arm/leg hair
) is really the least of your worries! Other things found in bags of tea include dead bugs, rocks, cigarette butts, bits of concrete, etc. Still, nothing dangerous. I'll bet you've brewed hairs before and just not realized it.
Sometimes I feel like it's a good thing too; it reminds us that there are real people farming and crafting these teas, and it's not just the enlightened/spiritual/esoteric stuff we like to imagine.
It is shocking the first time though! Welcome to the club.