If you could not get it back together with the spring in there then you were hung up on the alignment ridges.
In other words - It was not fully installed!!! You've probably worn out or broken something by now (maybe why it got loose!)
The pivot/alignment dowel has 2 seperate ridges that need to fully seat. (almost like stages) You definitely did not get it fully seated if you had to remove the spring assembly.
BTW - the B&M Shifter works far better with the centering spring assembly disconnected (but left on to take up the space - otherwise you get excess play)
Hate to be the bearer of bad news, but I would take it apart and access the mess...
