The door is suppose to lock (permanently) behind you, forcing you to go through the temple in order to get out. If you only have the one save slot, then there is no way back in (it is not an essential area, but you would miss experience and a bit of loot not doing it).

You could email the save to Larian (support@larian.com) and see if they will put your character back at the start of the temple; they did so for a couple people that fell through a forcefield and could not get back into an essential area, anyway.
Help...cant get to levers to lower force shields