Is it possible to get **** in a trial?

Trying to get Hecuba but don't want to have to repeatedly do runs just for her - saw somewhere that apparently you can meet Echo in trial chambers and get Hecuba there. However, every time i repeat one of the two fields trials I seem to have the exact same 'seed', room choices and everything. It may just be a matter of sample size(i've repeated each 3 times) - can anyone tell me if it's possible to get Echo?