I usually see this bug when I'm searching, but I'm not sure if it happens only with search. Sometimes I want to find an e-mail in the Trash folder, and when I do the search, it's not on the results. So, I click on the folder where the e-mail was (I'm not sure if I click on any folder it will have the same behaviour) and then in the Trash folder again, and the e-mail is there. I've seen this bug for a long time already.