Unfortunately, you would not be covered by the Home Buyer's Insurance if the property you are purchasing is subject to sealed bids.
What is a sealed bid?
When purchasing a property it is not always clear who you are going to be up against and there is always the risk of being outbid. If there is more than one offer made on a property, the estate agent could potentially request that all parties interested in purchasing submit a bid, normally in a sealed envelope. The highest bidder is normally declared the winner of the bidding process. The sealed bid system is conducted in complete secrecy.