First they said that Lois Lerner's e-mails were lost because her hard drive had crashed. No one who understands anything about information technology believed that one, since there are always system backups, and besides, e-mails are stored on a server, not on an individual machine.
They claimed they had made a herculean effort to recover the e-mails, but to no avail. When no one believed that, they finally relented and allowed someone who knew what they were doing to go in and find the e-mails. That was easy.