First I am terribly sorry to hear that your marker arrived in this condition, we pride ourselves on great customer service & attention to detail and in the rush to turn these things around we obviously missed the mark here.
Fortunately this is an easy problem to correct. The screw not being present allowed the bottom end cap oring to leak (possibly blow out all together). Just give me a ring or email at email@example.com
and I will get you the parts needed to make the repair out immediately.