There was no reason at all to mention race in the OP. All this bull about wanting the adcomm to be able to identify this woman doesn't make any sense, because if that is what the OP really wanted, then he would have written to the admissions office, or he would have called them, or gone through any of the normal channels of filing a complaint.
Whether the OP is or is not a racist isn't really at issue here. Likewise the issue isn't whether it's PC to identify someone as black. The issue is that it's obvious the OP would not have mentioned race if the woman was white. Whatever your actual reasoning was behind it, OP, it wasn't appropriate and you shouldn't be surprised that you came off as a racist.