I kind of wonder just how tunnel-visioned the main character can be. He/she knows that they just spent 210 years in cryo-freeze sleep. Some time during those 210 years, a stranger came, killed the spouse, and stole the infant. (And just why it is that the stranger thawed out the spouse's chamber AND the main character's chamber at the same is likewise bewildering.) That means that it is quite possible that Shaun grew up, died, and was buried more than a century before the main character was revived and escaped internment in Vault 111. Maybe it's possible to find Shaun's children/grandchildren. HOWEVER, taken as an infant, how would Shaun or offspring even know anything that transpired in Vault 111? Why would the abductor even consider telling Shaun that he had been abducted and his parent murdered by the abductor? So, when all possibilities have been considered, why the rush to go looking for Shaun? Sure, the main character may have an enormous parental concern, but is the character also so stupid to conceive that a LOT of time probably passed between the abduction and their revival?
It isn't until Mother Murphy states that via the Sight, she can see that Shaun is still alive. But note closely that at no time does she state just how old he is now.