I am not a cop and do not play a cop on TV but note that on NCIS and CSI a person can be detained as a material witness.
Perhaps Guccifer is cooling his heals as a material witness. His efforts and testimony are germane to the case along with his evidence
Guccifer has already been indicted here. You are exactly on target. The agreement with Romania says after 18 months he’s to be returned to Romania to continue serving his prison sentence. That screams witness.
have you stayed at a holiday inn express?