They knew when they asked the question.
Republican Rep. Tom Price asked the commissioner whether Lerner had a BlackBerry or mobile devices where the emails could be retrieved, Koskinen said he did not know.
I guess Rep. Price has his answer now, doesn't he?
http://www.freerepublic.com/focus/f-news/3172288/posts?page=22#22
Speculation on HOW issa’s committee knew about it:
either
someone on that To: list gave the email to issa’s committee
Or
Someone obtained the email by other means, and gave it to issa’s committee.