Bones are invisible in blender

Question

When I move the camera around in Blender the bones instantly go invisible however when I press 1 they're visible.

Answer 1

Seeing an object in axis aligned view, but not in user-defined view usually means it's far away from the current POV (point of view) or outside of the current frustum. Orthographic view provides no sense of depth. Objects appear the same size no matter how far or how close they are.

New objects are placed at the postion of the 3D Cursor.

The 3D Cursor is placed with LMB. A click in empty space will position it in a plane, that is parallel to the view plane at the distance of its old position.

A click on a visible object will project the 3D cursor on the object.

The current cursor position and the position of the selected object are shown (and can be changed) in the Properties Panel of the 3D View.

You can also use the Snap menu by pressing ShiftS.

E.g. with the object selected press ShiftS - Cursor to Center, ShiftS - Selection to Cursor to set the objects position back to the center.

Answer 2

It's layers. If you press 1, it's going to put you on the first layer. There are 10 layers, and 10 alternative layers. To access the layers, you can press 1, 2, 3, 4, 5, 6, 7, 8, 9, or 0. To access the alternative layers, you do the same thing but holding Alt. You can select multiple layers by holding down Shift and pressing those numbers.

And for assign an object to a layer, you have to select the object and then hit M. You can select which layer you want it on from there. The layers on the top are the regular layers, and the layers on the bottom are the alternative layers.