There is nothing better than when somebody tries correcting somebody on here, is a dick about it, and ends up being wrong. This one is even better than usual because Tier Three also liked your post showing he supported your incorrect attempt.
My use was entirely correct, and it is very easy to educate you as to why.
Let's say you have a friend name Jason. Jason has the guys over for a card game once a week. Before leaving your house to go to the house where your friend Jason lives, you say to your wife "Hey, I'm going over to JASON'S."
Even though the proper noun is "Jason" and not "Jason's," is saying "Jason's" wrong? No. Why not? Because it is implied that it is "Jason's house" you are referencing. Likewise, the proper noun is "Nordstrom" and not "Nordstrom's." However, saying "Nordstrom's" implies you are going to the Nordstrom store/location. The apostrophe shows ownership/possession. You are going to the house of Jason. You are going to the location of Nordstrom. Those are possessions.
Had I said "Nordstroms" without the apostrophe, you would have had a valid argument. But I didn't, which is why I used the apostrophe.
Now, go wipe the egg off of your face before going to Jason's (note the apostrophe).