750f rc24 drive sprocket nut broken inside?

[Rctwentyfourseven]

I recently changed the chain and sprockets on my bike. 
After a while, the drive sprocket bolt fell out. It seems too short, and a bit cut, and with some debris in the hole where the nut was, I am assuming it broke off inside and then screwed itself out. Now I am worried if the rest of the bolt is inside. I did some measurements of the depth of the hole and the length of the screw. Can anyone tell me how deep the hole should be and how long the bolt originally is?
The hole is 29mm deep
The entire bolt is 30mm long and has 9 rounds of thread. 
Also, what is the diameter of the washer? The original has disappeared, but if the bolt still works i could get a replecement if i just have the specs. 

[Terry]

This is what the sprocket bolt should look like:

 

[rhoderage]

Can you see a piece of it sheared off in the hole?  Shine a light and look for a matching sheared end to the bolt?

[DannoXYZ]

Bolts never break at tip, usually close to head. Most of stress is in first 2-3 threads.

 

Get replacement bolt and use torque-wrench to tighten it to spec.

A drop of blue Loctite wouldn't hurt.

[Rctwentyfourseven]

Thank you for the replies. Nice to know. I think it must have gotten a beating lying in between the sprocket and the sprocket cover or something.
I will try and get a replacement washer and use this bolt until i get a new original bolt and washer. 
Does anyone know the diameter of the washer?