No skeleton found when exporting

[Tompa9]

Hello,

 

I think I have already mastered some basic kitbashing in Blender. But I have same error when exporting again and again - no skeleton found. It happens, when I move for example head from original model onto my model, I´m trying to export it and this error appears. I thought that I dont have to move skeleton too from original model. Or I have to? Btw I haven´t deleted any skeleton from own model. It looks like disappear when I move parts from original to second layer. Thanks for help