A statement that the investigation did not establish particular facts does not mean there was no evidence of those facts.
...
Further, the Office learned that some of the individuals we interviewed or whose conduct we investigated — including some associated with the Trump Campaign — deleted relevant communications or communicated during the relevant period using applications that feature encryption or that do not provide for long-term retention of data or communications records. In such cases, the Office was not able to corroborate witness statements through comparison to contemporaneous communications or fully question witnesses about statements that appeared inconsistent with other known facts.
Accordingly, while this report embodies factual and legal determinations that the Office believes to be accurate and complete to the greatest extent possible, given these identified gaps, the Office cannot rule out the possibility that the unavailable information would shed additional light on (or cast in a new light) the events described in the report.