While Event Coins are listed as Quest Items, Event Vouchers, on the other hand, can be found in the Others tab of your backpack. If you've bought eggs or fossils from your vouchers, they end up in the Others tab as well. The Exp. Share obviously is a Held Item... If you have trouble locating your prizes in your backpack, and don't think you've got any new Pokemon to show for it either, my bet is that you've probably brought your eggs to one of the Daycare Centers, and that they're currently incubating, or are simply waiting for you to pick them up from there.