It was a secret Imperial document detailing the destruction of Caamas, (a planet of peace loving furry guys)buy Senator palpatine. a portion of the document was found in the ruins of the mount Tantiss store house. It almost sparked a civil war because it incriminated the bothans with sabatoging the Caamasi shield generators. Half of the NR wanted to punish the Bothans and Half the NR didn't. This was solved when Luke and Mara brought an entire copy of the document back from the chiss outpost of Niruan. This all happened in Vision of the Future and Specter of the Past by Timothy Zahn EDIT: fixed spelling EDIT 2: Took out Spoiler Room.
*Used* to be "Senator Palpatine"...has since been slightly retconned to "Chancellor-cum-President Palpatine," taking place sometime betwixt AOTC and Episode III.
I'd say that, all the Bothans involved that were still alive would be caught. most of them probably still lived on Bothawui and Kothlis content never to be found out.