I called the 800 customer service phone number and asked about a private sale. The woman I spoke with was very lovely and said she knew nothing about a private VIP sale. She took down my email address and phone number and promised to look into this and get back to me - after I hear back from her, I'll post a note!
I'm sure they are having private sale now, because there is a seller online who purchases clothing and everything for others and get commission from them, but she's getting commission like 25%, or a little more...
I called about a problem I was having with the website, and then asked about a sale. The gentleman I spoke with said if they ever have a sale it's open to the public. He said it's probably just a rumor and that the best time to check for sales is closer to Christmas.
I spoke with customer service at net-a-porter and they didn't know anything about a private sale but said that an actual sale at net-a-porter will be starting sometime later this week! They'll be emailing registered net-a-porter members so keep checking your emails!