C memcpy issues with unsigned char array

I have a question about memcpy that I hope someone can answer. Here's a short demonstrative program:

#include<stdio.h>
#include<string.h>
#include<stdlib.h>


int main (int argc, char **argv){
  unsigned char buffer[10];
  unsigned short checksum = 0x1234;
  int i;
  memset(buffer, 0x00, 10);
  memcpy(buffer, (const unsigned char*)&checksum, 2);
  for(i = 0; i < 10; i ++){
    printf("%02x",buffer[i]);
  }
  printf("\n");
  return 0;
}

When I run this program, I get 34120000000000000000.
My question is why don't I get 12340000000000000000?

Thanks so much