Does an Executed Limit Order Imply a Spot Price?
Think of all the limit orders waiting in line, first organized by price, and then by the time the order was placed (earlier orders are closer to the front of the line).  In order for your buy order to trade, there must be no other limit orders of 10.01 or higher, or the sellers order would have matched with them instead. So once your order is filled, the price is 10.00, even if just for a millisecond, because there was a trade at 10.00, even though the price might go right back up after the trade.