Investigators in both House and Senate were stunned late Friday when, receiving a batch of newly-released texts between FBI officials Peter Strzok and Lisa Page, they also received notice from the bureau that the FBI "failed to preserve" Strzok-Page messages from December 14, 2016 through May 17, 2017.

Given the amount of texting that went on between Strzok and Page, who were having an extramarital affair, that probably meant thousands of missing documents.

A number of critical events in the Trump-Russia affair occurred between December 2016 and May 2017, including:

Conversations between Trump national security adviser Michael Flynn and Russian ambassador Sergey Kislyak.

The completion and publication of the intelligence community assessment of Russian interference in the 2016 election.

The briefing in which FBI director James Comey told President-elect Donald Trump about the Trump dossier.

The president's inauguration.

The nomination and confirmation of new Justice Department leadership.

Flynn's interview with the FBI (conducted by Strzok).

Comey's assurances to Trump that he, Trump, was not under investigation.

A variety of revelations, mostly in the Washington Post and New York Times, about various Trump figures under investigation.

Attorney General Jeff Sessions' recusal from the Russia probe.

The firing of top Obama Justice Department holdover Sally Yates.

Trump's tweet alleging he was wiretapped.

Trump's firing of Comey.

And, finally, on May 17, 2017 — the final day of the missing texts — the appointment of Trump-Russia special prosecutor Robert Mueller.

Strzok and Page had a lot to talk about.

In a letter to Senate Homeland Security and Government Affairs chairman Ron Johnson, the Justice Department claimed the Strzok-Page texts were not recorded because of glitches in a changeover between models of FBI-issued Samsung Galaxy phones.

"Data that should have been automatically collected and retained for long-term storage and retrieval was not collected," the Justice Department said.

The FBI did send Johnson, along with Senate Judiciary Committee chairman Charles Grassley, hundreds of Strzok-Page texts that were successfully recorded. Some of those might prove as troubling as the first batch of texts, one of which discussed a mysterious FBI "insurance policy" in case of a Trump victory in the 2016 election.

In the newly-released texts, Strzok and Page discussed Trump winning the Republican presidential nomination, which they said would create "pressure" on the FBI to quickly finish up the Hillary Clinton email investigation, known inside the bureau as the "midyear exam," or MYE.

"And holy shit Cruz just dropped out of the race," Page texted Strzok on May 4, 2016. "It's going to be a Clinton Trump race. Unbelievable."

"What?!?!??" responded Strzok.

"You heard it right my friend," said Page.

"I saw Trump won, figured it would be a bit," Strzok said. "Now the pressure really starts to finish MYE."

"It sure does," Page responded.

Earlier, in February 2016, Page texted Strzok that candidate Trump "simply can not be president."

Senate and House investigators are scrambling to come up with a response to news of the missing texts. Part of that response will be consultation with Justice Department inspector General Michael Horowitz, who has been investigating the FBI's handling of the Clinton email investigation. Does Horowitz have those missing texts? Does anyone else?

The Senate and House will also be asking: Does the FBI's explanation make sense? Is there evidence to support it? Were other Samsung phones not recorded as a result of technical problems between December 14, 2016 and May 17, 2017?

And if the FBI's story checks out, is there still a way to find the missing texts? Who would have the power to do so? Horowitz's investigation is an administrative review, not a criminal probe, and does not have the authority to compel production of some information.

On Saturday, Sen. Johnson sent a letter to FBI director Christopher Wray with a series of questions about the missing texts. Does the FBI have records of any other communications between Strzok and Page? What texts has the FBI produced to the inspector general? How extensive was the alleged glitch that allegedly resulted in the lost texts?

Johnson also asked whether the FBI has "conducted searches of Mr. Strzok and Ms. Page's non-FBI-issued communications devices or accounts to determine whether federal records exist on those nonofficial accounts."

That is an apparent reference to instances in the texts in which Strzok and Page told each other that they were switching to iMessage for further conversation, suggesting they might have moved their discussion of sensitive topics from their government-issued Samsung devices to private Apple devices.

Underlying all the questions is a diminished level of trust between some quarters of Congress and the FBI.

"Very suspicious," said one investigator about the news. "Hard to believe," said another.

When asked to rate his trust of the FBI on a scale from 1 to 10, the investigator quickly answered, "Zero."