Several party members are in a dungeon together, but one party member has (perhaps foolishly) run off by themselves, and is now separated from the rest of the party by several hundred feet. This solo party member then encounters a monster and enters combat, but the rest of the party is too far away to be aware that there is combat taking place.

I'm wondering what is the best way to handle "combat time" in this situation:

• The solo party member rolls for initative and enters combat, but the rest of the party remain in free-form "narrative time". This accurately reflects the fact that the rest of the party don't know that combat is happening, but also allows the solo player to wait indefinitely on his turn until the rest of the party have time to catch up (e.g. moving their tokens on a VTT). This effectively means that time is moving at a different rate for different party members, which seems like it could cause problems.

• Everybody rolls for initiative. This solves the problem with inconsistent time tracking, and requires the rest of the party to use their turns to move their speed and catch up with the separated player. However it also implies that the rest of the party are somehow magically able to react quickly to combat that they cannot see or hear, which requires some suspension of disbelief.

• Only the separated player rolls initiative, while the other players enter combat with an initiative of zero. A compromise solution which allows time to be tracked in rounds for the whole party without implying the whole party is magically aware of being in combat. The initiative of zero reflects the fact that the rest of the party is unaware of combat and does not have a chance to react quickly.

I'm leaning towards the third option myself, but would like to know how others would handle this and if there are any better options (or if the rules specify a particular approach).