nothing extra happens.
If it can recoil a bit then it does so. If it can't then it presumably takes the -1 for being unable to recoil and if it survives then so be it.
However note that Ps being repulsed or recoiledcan pass through any friendly land troops facing in any direction - so this could only be causd by enemy or impassable terrain - which can only be S/L/WW, or a Rv if outside the allowed 45/90 deg angle allowed for wading.