The ask and Bid might not appear for a few reasons, sometimes the market makers will remove yesterday’s bid/ask to wipe the slate clean or it might just be a glitch.
What will tell you if there are any buyers and sellers is the volume. If a stock has say an average trading volume of 1 million transactions a day then you don’t need to worry about it. But if it only has a trading volume of 15,000 transactions a day then it might be hard to squeeze through.
Companies will only buy their stock back when they announce it or in special situations. If you place an order that cannot be filled for whatever reason the market will have to adjust to bring in more buyers or sellers to fill the order.
Brokers may also fill your order with their own accounts. A brokerage will keep extra money and securities around to help fill their client’s orders when no matching order can be found.
