Bruce was stunned when the 27-year-old England international handed in a transfer request within hours of the 1-1 derby draw with Newcastle on January 16 which led to his ?24million departure for Aston Villa days later.
He resisted the temptation to plough that money straight back into a replacement without having done his homework, despite having loan signing Danny Welbeck and Fraizer Campbell on the injured list.
Dream move: Darren Bent celebrates his recent goal against Manchester United
Instead, he pressed ahead during the remainder of the winter transfer window with his already planned moves for Stephane Sessegnon and Sulley Muntari.
But the process of finding a man to partner record signing Asamoah Gyan is now under way, and Bruce is promising to leave no stone unturned.
Bruce said: 'We have got Welbeck as one of our strikers and we have lost Bent, so you don't have to be a rocket scientist to know where we are looking to strengthen.
'We will look from now on. All our attention for the next three or four months will be to scour the world to try to find the right striker and the right person we can bring into the club.
'That's got to be our aim, to try to keep improving. That's got to be my job, to make sure that we keep improving as a club and keep improving as a squad.'
Bruce has made no secret of his desire to make Welbeck's stay at the Stadium of Light permanent, but he knows Manchester United boss Sir Alex Ferguson's has big plans for the youngster at the Old Trafford.
Sunderland looked to have banked a good price for Bent, but the flurryof activity with which the January window drew to a close saw pricesrise spectacularly.
Andy Carroll's ?35million switch from Newcastle to Liverpool opened the way for Chelsea to hand the Anfield club ?50million for Fernando Torres.
Like the Black Cats, the Magpies will wait until the summer, and Bruce knows they will not be the only two clubs looking for strikers during the close season, and that means players will be available.
He said: 'We will be looking, we will be looking at the market and scouring the market.
'But you have just seen how quickly things change in two or three days in England.
'What are Manchester City going to do? What are Chelsea going to do? Liverpool have done theirs. There will be players available. It is getting the right one.'
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