More likely to be just the light pressed steel guard around the disc. It is easily buckled so that it scuffs. If the disc was warped you would usually feel a pulsing through the brake pedal when applied.
Take it back to whoever fitted the bearing and ask them to have a look.
I was trained to test the disc for true after refitting using a dial test indicator, but not many places bother.
jack
November 2009
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