Conspiracy theory and repeating disinformation spread in 2017 in Belarus during the street protests. The disinformation message is consistent with recurring pro-Kremlin narrative about the Western attempts to instigate colour revolutions in EU neighbourhood.
Belarus 2017 Human Rights Report by the US State Department indeed does not mention this case. However the reason behind this is not a cover up as alleged in the publication but because the claim about opposition's attempt to conduct a terrorist act is unfounded and the charges were dropped by Belarusian investigators. At the same time the report mentions multiple arrests of opposition leaders by the Belarusian authorities: "Throughout the year Statkevich and Uladzimir Nyaklyaeu, another 2010 presidential candidate, opposition activist, and former political prisoner, were arrested repeatedly and placed in administrative detentions, usually in connection with unauthorized gatherings and demonstrations."
Statkevich team member Sergey Kuncevich was detained on 25 March 2017 and accused of transporting Molotov cocktails as part of a larger coordinated attempt to organize mass disorders. Nearly the same time Belarus' state-owned mass media (BelTA) published an article “Militants staging a provocation detained in Belarus” reporting about weapons allegedly confiscated from other accused. Investigators found no evidence to confirm accusations and the criminal prosecution of all those arrested in relation to the case was closed in late November 2017.
See earlier disinformation cases alleging attempts to destabilize Belarus using Ukrainian weapons here and here.