That bolt is a stud used for locating the pump on the head, it only has a 7lb or so torque spec and (as you found out) it is easy to snap off. Mine was broken off before I got to it. The nut does not to be there as it is only used to hold on the pump until the other bolts are torqued down. AS long a there is enough to locate the pump on the head you should be fine. I'm sure you could find a replacement also.

 

Thanks for the input, guys. I just got done putting everything back and taking a test drive. So far, the street under my new parking spot is dry and has been for about 2 hours. I hope this holds up.