It's a little complicated, but it appears the Justice Department's inspector general, Michael Horowitz, has uncovered a serious problem relating to the anti-Trump texts exchanged by two former top FBI investigators, Peter Strzok and Lisa Page. Here is what Horowitz lays out in a new report:

Shortly after being appointed in May 2017, Trump-Russia special counsel Robert Mueller hired Strzok and Page. When he did so, he issued them work iPhones. A short time later, Horowitz, who was investigating the department's Hillary Clinton probe, discovered that Strzok and Page, using their old FBI phones, had exchanged virulently anti-Trump text messages. Horowitz told Mueller, who thought the situation serious enough to remove Strzok and Page. Yet it appears the Mueller office stripped Page's iPhone of all data without ever checking on its contents, and they stripped Strzok's iPhone after a perfunctory check that may or may not have taken note of the content of its text messages. When Horowitz asked for and (belatedly) received the phones, he could recover nothing from them.

Horowitz explains the situation in a brief report, "Recovery of Text Messages From Certain FBI Mobile Devices," which was released last week. Here, in a little more detail, is what he found:

During the investigation into the Hillary Clinton email affair and early Trump-Russia probes, Strzok and Page received FBI-issued Samsung Galaxy S5 phones, which were later replaced by Samsung Galaxy S7 phones. Some of the well-known problems with retaining many of their texts, anti-Trump and otherwise, arose from the failure of the FBI to archive texts after the S5-to-S7 changeover.

Mueller was appointed on May 17, 2017. Strzok and Page joined the investigation shortly after and were issued special counsel iPhones. They apparently used those phones in addition to the Samsung S7s, which they still had.

As that happened, Horowitz was conducting his Clinton email investigation and discovered the anti-Trump texts. Horowitz told Mueller about the texts, which showed Mueller's top investigators harbored a deep anti-Trump bias. In July 2017, Mueller removed Strzok and Page from the investigation.

One might think that, given the reason for the removal, Mueller might want to check the content of the Strzok and Page iPhones. How could he not, when the whole reason he fired them was because of the text messages that were discovered? If an official finds out he has a major problem with key staffers, a problem serious enough that they have to be removed, how did he not check to see how big the problem might be?

Certainly that is what Horowitz thought. "In view of the content of many of the text messages between Strzok and Page, the [inspector general] also asked the special counsel's office to provide to the inspector general the Justice Department-issued iPhones that had been assigned to Strzok and Page during their respective assignments to the special counsel's office," the Horowitz report says.

It wasn't that simple. Instead, this is what happened to the iPhones, according to the Horowitz report:

Page left Mueller's office for good on July 15, 2017. The Mueller office did something called an exit clearance certification, but the Mueller official in charge told Horowitz she did not receive either Page's iPhone or her laptop. According to Horowitz, Page told the official "that she left her assigned cellphone and laptop on a bookshelf at the office on her final day there." That is not ordinary procedure when an official leaves a highly sensitive investigation.

The Mueller official found the laptop but not the phone. Then in January 2018, after the Strzok-Page texts had become big news, Horowitz asked for the Page iPhone. Mueller's office couldn't find it. It was not until September 2018, not long ago, that they finally located the phone and gave it to Horowitz. Horowitz's experts discovered that the phone had been stripped of data — "reset to factory settings" — more than a year earlier, on July 31, 2017. Horowitz could find no data at all related to Page.

"Neither the [special counsel's office] nor [the Justice Department] had records reflecting who handled the device or who reset it after Page turned in her iPhone on July 14, 2017," Horowitz wrote. "[The special counsel's] Records Officer told the inspector general that she did not receive Page's phone following her departure from [the special counsel's office] and therefore did not review it for records that would possibly need to be retained prior to the phone having been reset."

Strzok left Mueller's office in late July 2017. According to the Horowitz report, he completed his exit clearance certificate on Aug. 11. "As part of an office records retention procedure, the [special counsel] Records Officer stated that she reviewed Strzok's phone on Sept. 6, 2017," Horowitz wrote. "She told the [inspector general] that she determined it did not contain records that needed to be retained. She noted in her records log about Strzok's phone: 'No substantive texts, notes or reminders.'" The officer told Horowitz she did not remember whether there were any texts on Strzok's phone beyond the notation "no substantive texts."

Mueller handed the Strzok phone over to Horowitz's investigators in late January 2018. "By that time, the device had been reissued to a new user," Horowitz noted. Horowitz's office "conducted forensic analysis of the iPhone and determined that it had been reset to factory settings and reconfigured for the new user to whom it was assigned. It had no content related to Strzok."

The Justice Department told Horowitz that it "routinely resets mobile devices to factory settings when the device is returned from a user."

The iPhone affair leaves some real questions. How did Mueller not see the need to examine the Strzok and Page iPhones after Mueller learned of the anti-Trump texts they had sent with their FBI phones? If the texts were serious enough to fire Strzok and Page, were they not serious enough to warrant a search of the phones? How did Mueller not see the need to immediately hand the phones over to Horowitz, who originally informed Mueller about the Strzok-Page text issue? And what did the special counsel's declaration of "no substantive texts" on Strzok's phone mean, given that the Justice Department had earlier withheld many relevant Strzok-Page texts from congressional investigators? Finally, what does Mueller's behavior in the text situation say about his willingness to submit to oversight, even by the Justice Department's own inspector general?

It is likely that the public will hear more about this in the future. Horowitz obviously thought the iPhone issue was important enough to issue a formal report about it, instead of simply briefing Congress or writing a letter to a committee with oversight authority. The iPhone question could well be included, and perhaps expanded upon, when Horowitz releases his report on aspects of the Trump-Russia investigation, maybe later this year. Until then, the text questions will remain unanswered.