it was hiding in pakistan in a large mansi..... ummm i mean. lol
no actually. we are not talking about dark matter but regular matter that should be left over from the big bang. it has bothered scientists for years and now a student on a break has figured it out and found the missing matter. called "filaments", they are hiding in plain sight sort of thing. to get all the details and a clear explanation, read here:
http://www.cosmosmagazine.com/news/4358/aussie-student-find-missing-mass