What "happened to you yesterday"? How do you know that it was a market maker selling its own shares to you, and not simply representing an individual's order? It is not possible to know that without speaking to the trader yourself.
Occasionally a trader at a market maker will trade for his own account. I sometimes trade through a MM who has occasionally followed me into a stock if he liked the idea. And MMs do provide liquidity when there are no individuals bidding or offering, but when that happens MMs almost always sell short first on the offer and then go high bid to cover. They try to end each day flat, or as close to it as possible, and as a rule they will not tie up their capital on penny stocks.
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