I just want to add on to Hot Licks's point in the comments section.
Supply of oil provided by the petrol stations are not real-time. In a way, you could say that they probably have enough to cover for the oil demand for the month. Now assuming there is this increased demand that you observed. The consumers are buying the oil ahead of their needs, probably up to the month's needs, for fear of future price hikes.
Now why does this not cause an increase in price? The demand of oil simply had not exceeded the supply enough to cause a price hike. This is where there is a disconnect between theories and practical. You are assuming the petrol stations match their supply to the equilibrium demand at any given point in time, such that the increase in demand as you observed, would create demand in excess of the current supply, resulting in increased prices. Which is not the case in reality since they likely still have the supply to cover the increased demand.
Also, how do you define increased demand as an individual entity? the only group able to do that should be a legitimate statistical body or the producer themselves. As such, we as individuals are unable to determine if the increased demand are really large increases or just a small insignificant spike.
As this is a supply shock, the increased demand resulting is a one-off type of thing and it does not affect the longer term equilibrium. It would be seem excessive for firms to increase prices based on that. If they did, once the issue is resolved, the price hikes could quickly backfire and cause lower demand. Note that in this case we are talking about oil, the demand would not necessarily go lower, but imagine the backlash from the consumers.
But in all, I do agree that government regulation of the oil prices have a hand in this because well, oil is a "sensitive" commodity.