Been there, done that and, not sure now, but I think I have a T-shirt for each time I goofed.
It is so easy to miss this or that when the excitement of a good find plants itself square in your face. This Torpado had suffered some trauma, but I did find out before making the purchase. The damage actually helped lower how much I had to pay - a lot...
And, though I did NOT notice it at the time of purchase, my Marinoni Piuma had suffered minor damage. A wee dent on the top tube. Disappointed? Absolutely! But the Marinoni is such a nice rider that the dent is not really an issue. After all, the bike is not vintage, in my book of what is and what is not vintage...
As for the OP's Trek, keep it and ride it, assuming the bike still feels like it is worth what you paid. If not, send it back or seek some form of compensation.