I think I figured it out. For folks running Yosemite, right click on the Inbox icon. At the bottom of the contextual menu that pops up, choose, “Get Account Info”. A new window will open called “Account Info”. At the top of the window is a drop down list of all your email accounts. Under that drop down list are four tabs. Choose the second one, “Mailbox behaviors”. There are four mailboxes listed, drafts, sent, junk, and trash. YOu will be looking at the Trash section. Go through each email account. If the option to “Store deleted messages on the server" appears, UNCHECK that box. Then close the little window. Your trash can should reappear.