I bought yesterday the Ramirez expansion pack, and in his rules booklet it's said that the Hound D.o.G.'s rules and statistics are printed on a separate sheet. Well, OK, the drone has its own character sheet and there are rules on the scenario pages on how to assemble and remote control it, but inside the box there's nowhere I could find the rules regarding shooting, operating or otherwise anything more specific.

Any hint? Did I get a faulty expansion box?

If I remember correctly, the original rules for the drone are on the back of its character sheet. If you want to get the revised rules for it, they are only available in the Revised Rule Book.

DOH! Never thought of looking on the back of the character sheet… maybe I need to get more sleep.

Don't worry. After all, who in his right mind would guess that the rules for a character are printed on the back of that character's character sheet so you have to remove all tokens and turn around the sheet if you want to check the rules during game play. Not exactly a brilliant idea.