Hmm, then you may want to try help->check for updates to see if you get a parts database update. It is supposed to be automatic at each start but I have had cases where a update was available but didn't load til I clicked the check for updates button. For me searching for either lm2596 or rio rand brings up the part (note you have to hit enter to actually make the search, clicking doesn't start search) as I think the rio rand was a recent update. Any way you can get a part that is acceptable to you is a good way to get a part 
so if what you are doing is working keep going.
Peter