Not to cause any angst, but Senators Feinstein’s nomination staff is administratively challenged. You are a constituent and a very simple, “we have received your nomination application which will be given all due consideration”, would be nice. One would also think that returning a self-addressed postcard is easy enough, but don’t hold your breath. If you are asked to send another packet, I'd suggest that it be sent by certified mail with return receipt requested. Consider emailing Senator Feinstein's staff so that you have an established electronic trail. Hoping that some staffer will answer the phone in California is fruitless.
Make sure that you have applied for all the nominations sources eligible in the event you aren't a Senatorial nominee. Also, you might receive a call from either senatorial staff late this year regarding your nomination. They will inquire if you already have a nomination. If you do have a nomination, the staffer may tell you in so many words, the one (nomination) you have is “good enough”. End of “interview”. Neither Senators like doubling up on nominations and prefer to spread the wealth.
Good luck in your quest for a nomination and appointment.