They just accidentally reset the phones.
Via Daily Caller:
President Donald Trump criticized the lack of media attention on new revelations about former FBI employees Peter Strzok and Lisa Page from the Department of Justice, in a series of Sunday morning tweets.
The Inspector General’s office of the DOJ revealed Thursday that it was unable to recover thousands of text messages sent between Strzok and Page through the course of their employment during the 2016 presidential election. Strzok and Page were carrying out an affair at the time of their employment while also playing central roles in the investigations of the Trump 2016 campaign and special counsel Robert Mueller’s investigation.