The West Brom striker seemed to be on his way to the KC Stadium in a club-record deal on transfer deadline day but the Baggies pulled the plug with just an hour of the window remaining.
It was a messy situation, with Long having left a Republic of Ireland get-together on a charter plane laid on by Hull as talks continued.
West Brom released a statement in the aftermath of the aborted transfer suggesting Hull had changed the terms of their initial bid, but a frustrated Bruce, addressing the issue for the first time ahead of Saturday's Premier League clash with Cardiff, felt the clubs must have been close to getting the deal over the line.
"I'm obviously bitterly disappointed that we didn't get Shane Long," said Bruce. "That would have been the icing on the cake in terms of the squad we're trying to get together. We thought at one stage we were really, really close.
"He left the headquarters of Ireland, he didn't get on a plane until 6.30pm, then I picked him up at Leeds Bradford Airport at 8.15pm for a medical at 9pm.
"It was being battered back and forward (between the clubs). I've seen that happen over days, weeks and months and I knew dialogue was going on, but we must have been there or thereabouts (on valuation) or why would they let him go on a plane? Why would he be doing a medical if there was no chance of it happening?
"But unfortunately it didn't happen. That's West Brom's prerogative, he's their player and they changed their mind for whatever reason.
"I'm sure Shane is as disappointed as anyone, stuck at our training ground, left high and dry effectively."
Bruce was able to agree a deal to bring Egyptian striker Gedo back to the club on loan from Al Ahly, joining fellow recruits Danny Graham and Yannick Sagbo, but a renewed bid for Long could still be on the cards in January.
"It would have been great for us if it happened, I'm a big admirer of the boy," he said.
"I've seen how disappointed he was, left the way he had been. That's football and you never know what will happen in the next three or four months but if he became available again of course I would be interested."
Despite the final move for Long falling apart, Bruce successfully re-shaped his promotion-winning side during a busy summer.
He strengthened his squad in every position, bringing in 11 new additions and catching the eye when he persuaded England caps Tom Huddlestone and Jake Livermore to swap Tottenham for Hull.
But through the loan market and free transfers he was able to do so on a budget of less than £15million.
"We can't complain," he added. "I was at training today and I said 'what a difference to 12 months ago' to the squad of players we have here.
"No disrespect to what has come before but that is when you recognise what the Premier League does. It forces you to bring in bigger and better players."