Most stars are born in groups or clusters of anywhere between 100 and millions of stars. Most of these groups and clusters do not survive more than about 10 million years or so and the fraction that survive decreases further with time.
There are two basic reasons. First, it seems that most young clusters and associations may be born in an unbound state. Second, those that are gravitationally bound can become unbound through the expulsion of gas or through tidal interactions with the Galaxy, spiral arms and giant molecular fields. A supernova is one event that might be a culpable agent in expelling mass from a young cluster and consequently unbinding it.
It is therefore highly unlikely that a 4.5 billion year old star will be found in a cluster. There are very few examples of clusters at this age or older.
As an aside, the theory that the Sun was born from the debris of just one or even a few stars is totally false and easily disproved by looking at the isotopic composition of dust grains formed in other stars before the solar system was born. These can be found inside meteorites and demonstrate that the solar system contains debris from many, many stars; of both high and relatively low masses.
See How can there be 1,000 stellar ancestors before our Sun? and Parent stars of our Sun - Where are its remains?
Edit: It seems that you are just asking why we can't see siblings of the Sun, including this massive star that may have been involved in the formation of the solar system.
First - it isn't clear that the Sun was born in a cluster from material seeded by a supernova from another star in that cluster. There is a timing problem. The massive star that exploded would have to form more than 10 million years before the Sun. Clusters we see today do not seem to have such an extended star formation history.
Second - even if that weren't the case, a supernova very frequently gives rise to a "kick". The velocity dispersion of pulsars (recent supernova remnants) is exceedingly large (100s of km/s). Many remnants would escape the Galaxy and there is no chance of predicting where they would be in billions of years.
Thirdly - even if the first and second problems were not applicable, as I mentioned above, even bound clusters do disperse. Once free of any binding potential stars can undergo a process called "disc heating" - the action of encounters with spiral density waves and giant molecular clouds gradually increases their velocity dispersions (changing their kinetic energies and exerting torques that can change their angular momentum wrt the Galactic centre). This allows the solar siblings to go their separate ways. A Galactic orbit at the solar radius is more than 200 million years. A velocity difference of just 1 km/s (typical in a cluster even before it unbinds or is heated) could result in a separation by 200 pc in that time. The Sun has executed more than 20 such orbits.
