Instead of just agreeing with you and not really not giving you suggestions on how to actually avoid this particular situation. Here is what most likely happened and what you can do to avoid this in the future.
You probably used your Debit Card and entered your PIN AT the Gas Pump. When you do this they place a $75 hold to cover any gas you MAY pump. If you actually got to $75 you would notice that the pump would have stopped. Normally this hold should be removed as soon as the final amount was submitted. However, due to certain circumstances usually with the Gas Stations merchant account processor it may not be removed until a later date.
In order to avoid this possibility (at any gas station) you need to go inside the station and get the gas for a specific amount. They will then charge you that set amount with no additional holds.
By the way this can happen at other places as well. For example it can happen at places such as Hotels, Rental Cars. It can also happen at restaurants if you do something like run a tab. But a restaurant can not over-authorize a card to cover things such as possible tips.