In Shia Islam there is this belief that there has to be one hojjat of Allah on Earth. He could be described as the
Further description found in the question Sunni viewpoint about "vasi" or "hojjat" in each era?
The way it is described, it seems that this presences is ensured by Allah Himself.
There is also this belief that Mohammad(saww) went on a maraaj in which he went to the skies, beyond the point which Gabriel(as) couldn't go and had words with Allah.
Now, since Mohammad(saww) was than Allah's hojjat on Earth, so when he went to maraaj who was Allah hojjat on Earth?
I don't find the presence the Ali(as) on Earth as a sound explanation because he at that time was not the Imam, the hojjat (maybe that's incorrect) because Mohammad was still alive.
It's is said that when Mohammad(saww) got back from maraaj things were in the exact same position and condition the way they were when he left (the door chain still swings, the warmth on bed or door knob (not sure)). Which, scientifically speaking, could mean that he went and came back in zero time and therefore no time passed when there wasn't a hojjat present on Earth. Is that a possible and a valid explanation?