I have searched for the answer to this but have found nothing specific.
How high above ground should this be and should it have a threaded cap.
In my area, the cleanout does not have to be above ground nor does the cap need to be threaded.
ditto 
tritto
What kind of cap was that? Looked like concrete.
The cap is a push on 4" with a bunch of dirt on top.
That is probably why I cannot find a code, there is not one.
Thanks
The cap is just a push on pvc 4", with dirt on top.
I probably can not find code because there is not one.
thanks
Same here. No need to be above ground and no requirement to have a screw on cap.
If the cleanout is too far out of the ground, it usually gets trimmed by a mower, and I have seen that. In some cases, they end up buried.