West Brom striker Long 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 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."
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