interesting tactic from a seller
 

I had an over priced T206 Tolstoi in my watch list and with an hour left it had a bid, no big deal that person can have it. I checked a couple hours late and it was "unsold" with no bid retractions.

Do sellers use separate accounts to "bait" watchers into bidding then cancel the bid w/o leaving a trail?

There is no way you can cancel a bid with a few hours left.

Yes sellers use separate accounts do you what you described but they cancel the sale and relist.