Well, your back one is the intermediate servo which is third gear. I'm not a transmission expert, but maybe the band was not adjusted properly and the piston got forced out. If part of the case is damaged and you cannot hold the snap ring in, then you are probably going to need a new case (which means a rebuild). If it bled a lot of fluid out and any of the internals seized up, then you may have many more problems.

If it was a recent install, then hopefully the transmission is under warranty and you can get another, especially if there is a defect in your current box. Hope it works out OK, keep us posted!