Had Adams, or another GM, offered to take the Boychuk contract last year, they might have gotten a second or third+. But why would the Isles make such a move now?
Boychuk has already received his last two signing bonus payments, the bulk of his remaining money, presumably from the Isles and whatever insurance covered. He only has $1.25 million remaining on his salary this season, with insurance covering perhaps as much as 80% of that, leaving around $250,000 due (maybe a bit more, but it is still a de minimis amount). It is nothing in terms of real money.
Meanwhile the Isles had their payroll inline for the season and around $2.2 million available in LTIR space for an add at the deadline. If they were going to attach an extra second rounder to a deal, they would probably give it to the team they are trading with for reinforcements, and ask them to retain and/or take back Uncle Leo or Hickey to offset any remaining salary cap imbalances.
This is a deal that helps both teams. The Isles get off LTIR, to accrue more space, and the Sabres can now essentially trade whoever they want, at the pittance of paying out maybe as low as $200,000 in real money. Adams just saved his owners a boatload of money, if they have a firesale, by not having to take on salary in return.
The Boychuk contract has significant value and there aren't many contracts like it available in trade. Lou knows it and sold accordingly.
Adams was smart not to haggle and potentially cost his owners a LOT of real money down the line, by potentially having to retain or take back significant salary. He had little leverage, since this is the best outcome for him and potentially making more trades, plus at least staying in the good graces of his employers.