Well Trip's 'death' was actually supposed to be explained in Season 5 in more detail... along with in the books The Good That Men Do
and Beneath the Raptor's Wing
For reasons that remained classified for (approximately) 250 years, Tucker was forced to fake his own death in 2155, days before the foundation of the Coalition of Planets, precursor to the United Federation of Planets.
In files de-classified in the early 25th century, it was revealed that Tucker had been recruited by the rogue spy agency known to some as Section 31 to infiltrate the space of the Romulan Star Empire and sabotage the Romulans' research into developing a Warp-7 stardrive.
Tucker returned to Romulan space shortly after the formation of the Coalition of Planets in order to gather intelligence on the Romulans before the inevitable war with the Empire broke out. At some point the historical record was altered, changing the date of Tucker's "death" from 2155 to 2161.
Tucker survived under the assumed name of Michael Kenmore, and had several cosmetic alterations done to his face to ensure his anonymity. He moved with T'Pol to Vulcan, and eventually became the father of her two children: T'Mir and Lorian, named after his son from an alternate reality. This was not common knowlege, however, and most people believed they were the result of her reconciliation with Koss years later. He lived with them in T'Pol's ancestral home, but posed as her gardener.
The book events were supposed to be referenced/occur in SEASON 5!!!!!
I never heard this, I'm ... speechless. Sorta.