They did
https://www.cnn.com/2018/07/03/politics/strozk-lawyer-subpoena-cnntv/index.html
https://www.washingtontimes.com/news/2018/jul/9/lisa-page-fbi-lawyer-who-texted-peter-strzok-subpo/
Ignoring it is not the answer. The short answer to this is that a subpoena is a legally binding court order for you to appear in Court. Failure to abide by a court order can result in a finding of contempt. A finding of contempt can result in jail time.