So a couple of months ago I noticed that there was a long strand of floss that had caught on the shower drain. It had wrapped itself around the grate and the ends were hanging down into the pipe. I pulled it out so it wouldn't wash away and when I did, about two heads' worth of hair came with it. It was completely gross, yet so oddly satisfying, like pouring out a bucketful of black water after shampooing the carpet (I swear they put black dye in that machine).
I replaced the floss with another strand, this time making it really long and tying it in a knot on the grate so it wouldn't accidently wash down the pipe and collect all that hair underground. Works like a charm, and now we can cancel my daughter's buzz cut appointment and let her keep her long (see photo above) beautiful hair.