Seized intake cam please help
 

I have an na Miata (1.6L long nose), and after letting it idle for a few minutes the other day the intake cam completely seized. I removed the cam and I can see that at the very front surface it has grinded and seized. My first thought was my oil pressure was too low or something. But I checked the other sections down the line of the same camshaft, and they all look perfect, not even signs of high heat. Does anyone know what could have gone wrong? I have a new head ready to throw on but I don't want the same thing to happen.
https://cimg0.ibsrv.net/gimg/www.mia...1c56f81100.jpg
https://cimg3.ibsrv.net/gimg/www.mia...c8a9c6cb66.jpg
https://cimg1.ibsrv.net/gimg/www.mia...ac5b2cfaa0.jpg
https://cimg2.ibsrv.net/gimg/www.mia...340dbb4f2b.jpg

Done any work on it lately? That might provide a clue.

I'd check the oil gallery to that journal, might be blocked/obstructed.