Testing if an instance of this object with a certain instance variable value exists

I'm making a random level generator, and I assign two special room with the instance variable order as "start" and "end". But from the random nature of my gen system and the way I delete duplicate rooms on the same coordinate, there's a small chance the start room will be overlapped by other rooms (including the end room)

What I want to do is, after there's only one room per grid position (done, working fine), I test if there's a room with the instance variable order = "start" and, if false, restart the gen process.

If it helps, I understand the (condition ? returniftrue : returniffalse) expression, so if the solution uses it I'm not afraid to try.

You can use system pick by evaluate : pick all room objects where room.order=start, set a local or global variable to room.pickedcount. Then you say if the local or global variable = 0 (i.e. there are no rooms with order set to start) then restart the process.