That model has hydrostatic steering, if the loader was working fine then the steering controller should be getting the proper pressure and flow.
Where you able to turn the steering wheel yet the wheels on the tractor wouldn't turn, and yes it could still have even really good resistance in doing that? That would be a blown seal.
Or did the steering wheel come to a stop and not budge at all? That would be a controller or hydraulic feed issue.
Most if not all the times I've heard of this is because the Cylinder that steers the tractor has a blow center seal, no you won't see a fluid leak, as it just leaks fluid back to the other line and back to the tank.
Yes it could also be a mechanical issue, like a worn or dry bearing on the axle pivots.