"In addition to that, federal agents are asking to keep the $3,030,000-worth of Bitcoins that the government collected from Slomp, and which have already been converted into cash."
It would be interesting to know how and when the conversion was made. (Presumably that happened after November/2013, so it would be about 3'000 -- 6'000 bitcoins.)
Posters in other threads who seem to be well-informed claim that Ulrich's bitcoins will surely be sold through public auctions, which is what the government must do with seized goods. But it seems unlikely that they auctioned Stomp's coins, that would have been noted and widely reported.
Perhaps the federal agents considered bitcoin a currency, not goods, at the time? Perhaps the coins had already been converted to cash by Stomp or "J" when they were arrested?