Tom no es consciente de lo que ha pasado.

English Translation

Tom is unaware of what has happened.

would “ignora” work?

English Translation

Tom is unaware of what has happened.

“no es consciente de” (is not aware of) or “no se da cuenta de” (does not realize) work here but I would say not “ignora”. Ignoring (what has happened) conveys the idea that Tom is aware but chooses to ignore it.