Did Thomas Hobbes believe the social contract was an actual historical event?

No, Thomas Hobbes did not believe the social contract was an actual historical event.

While Hobbes utilized the concept of a social contract to justify the necessity of political authority and the state, he recognized that his theories regarding the contract and the state of nature were unhistorical. He did not assume that there was ever a real moment in history when individuals gathered to make a mutual promise to delegate their self-government to a sovereign.12

Instead, Hobbes presented the social contract as a useful, hypothetical framework. By conceiving of the state as if it had resulted from such an agreement, he sought to clarify timeless political problems and demonstrate why rational individuals would choose to trade their liberty for the security provided by a sovereign power.12