The Lions looked to be in cruise control before Scotland Under-20 winger Ryan Fraser curled a shot inside the post in the 43rd minute.
The Cherries scored their third in the 54th minute when Harry Arter smashed home a loose ball on the edge of the box.
Substitute Brett Pitman dispatched a second penalty in added time after Fraser had been fouled.
It was a bad day for Lomas' side who fell to their second heavy defeat in four days after going down 4-0 at Birmingham in midweek.
Lomas said: "There were some poor decisions from the referee, including the red card to Dunne. How was that a deliberate handball?
"It's one thing to give a penalty for that incident but another thing to send him off and it was very harsh as he had no way of winning the ball.
"The referee booked every tackle we made but did nothing about the tackle by Fraser on one of our players.
"The goal just before half-time gave Bournemouth some confidence and momentum. We were hindered by the refereeing decisions but we did not help ourselves.
"Bournemouth's second goal was a free header and you shouldn't be giving goals like that away at this level.
"The first half was good but now we need to pick ourselves up and get over this because it was disappointing after going ahead and being on top for 40 minutes."